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• Hourly SQL Server 2005 Slowness (Possibly caused by SYSTEM)

  - by Zorlack

  We're trying to diagnose the cause of slowness on our Database server. We're running the latest rev SQL Server 2005 on Windows 2008x64. The behavior that we're seeing is this: We see the SYSTEM process spike one of the CPUs for about 2 minutes, during this time SQL server slows down by a factor of 10. The slowness lasts until SYSTEM is done, then in an hour everything starts again. During these slowdowns disk writes don't spike, paging doesn't spike, the only noticeable precursor we see is that SYSTEM maxes out one of the sixteen (HT)CPUs. Note that this doesn't happen at the top of the hour, it just happens once an hour, and it shifts a bit depending on the length of the incident. At the moment this is causing intermittent slowdowns, but when the server is really busy it can cause Worker Thread starvation. The server is a Dual Quad Dell R710 with 96GB of RAM and RAID10 data/log disks. Has anyone experienced this kind of problem? Does anyone know where we should look? Edit: SQL Server Version is 9.0.4035

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• Azure Diagnostics wrt Custom Logs and honoring scheduledTransferPeriod

  - by kjsteuer

  I have implemented my own TraceListener similar to http://blogs.technet.com/b/meamcs/archive/2013/05/23/diagnostics-of-cloud-services-custom-trace-listener.aspx . One thing I noticed is that that logs show up immediately in My Azure Table Storage. I wonder if this is expected with Custom Trace Listeners or because I am in a development environment. My diagnosics.wadcfg <?xml version="1.0" encoding="utf-8"?> <DiagnosticMonitorConfiguration configurationChangePollInterval="PT1M""overallQuotaInMB="4096" xmlns="http://schemas.microsoft.com/ServiceHosting/2010/10/DiagnosticsConfiguration"> <DiagnosticInfrastructureLogs scheduledTransferLogLevelFilter="Information" /> <Directories scheduledTransferPeriod="PT1M"> <IISLogs container="wad-iis-logfiles" /> <CrashDumps container="wad-crash-dumps" /> </Directories> <Logs bufferQuotaInMB="0" scheduledTransferPeriod="PT30M" scheduledTransferLogLevelFilter="Information" /> </DiagnosticMonitorConfiguration> I have changed my approach a bit. Now I am defining in the web config of my webrole. I notice when I set autoflush to true in the webconfig, every thing works but scheduledTransferPeriod is not honored because the flush method pushes to the table storage. I would like to have scheduleTransferPeriod trigger the flush or trigger flush after a certain number of log entries like the buffer is full. Then I can also flush on server shutdown. Is there any method or event on the CustomTraceListener where I can listen to the scheduleTransferPeriod? <system.diagnostics> <!--http://msdn.microsoft.com/en-us/library/sk36c28t(v=vs.110).aspx By default autoflush is false. By default useGlobalLock is true. While we try to be threadsafe, we keep this default for now. Later if we would like to increase performance we can remove this. see http://msdn.microsoft.com/en-us/library/system.diagnostics.trace.usegloballock(v=vs.110).aspx --> <trace> <listeners> <add name="TableTraceListener" type="Pos.Services.Implementation.TableTraceListener, Pos.Services.Implementation" /> <remove name="Default" /> </listeners> </trace> </system.diagnostics> I have modified the custom trace listener to the following: namespace Pos.Services.Implementation { class TableTraceListener : TraceListener { #region Fields //connection string for azure storage readonly string _connectionString; //Custom sql storage table for logs. //TODO put in config readonly string _diagnosticsTable; [ThreadStatic] static StringBuilder _messageBuffer; readonly object _initializationSection = new object(); bool _isInitialized; CloudTableClient _tableStorage; readonly object _traceLogAccess = new object(); readonly List<LogEntry> _traceLog = new List<LogEntry>(); #endregion #region Constructors public TableTraceListener() : base("TableTraceListener") { _connectionString = RoleEnvironment.GetConfigurationSettingValue("DiagConnection"); _diagnosticsTable = RoleEnvironment.GetConfigurationSettingValue("DiagTableName"); } #endregion #region Methods /// <summary> /// Flushes the entries to the storage table /// </summary> public override void Flush() { if (!_isInitialized) { lock (_initializationSection) { if (!_isInitialized) { Initialize(); } } } var context = _tableStorage.GetTableServiceContext(); context.MergeOption = MergeOption.AppendOnly; lock (_traceLogAccess) { _traceLog.ForEach(entry => context.AddObject(_diagnosticsTable, entry)); _traceLog.Clear(); } if (context.Entities.Count > 0) { context.BeginSaveChangesWithRetries(SaveChangesOptions.None, (ar) => context.EndSaveChangesWithRetries(ar), null); } } /// <summary> /// Creates the storage table object. This class does not need to be locked because the caller is locked. /// </summary> private void Initialize() { var account = CloudStorageAccount.Parse(_connectionString); _tableStorage = account.CreateCloudTableClient(); _tableStorage.GetTableReference(_diagnosticsTable).CreateIfNotExists(); _isInitialized = true; } public override bool IsThreadSafe { get { return true; } } #region Trace and Write Methods /// <summary> /// Writes the message to a string buffer /// </summary> /// <param name="message">the Message</param> public override void Write(string message) { if (_messageBuffer == null) _messageBuffer = new StringBuilder(); _messageBuffer.Append(message); } /// <summary> /// Writes the message with a line breaker to a string buffer /// </summary> /// <param name="message"></param> public override void WriteLine(string message) { if (_messageBuffer == null) _messageBuffer = new StringBuilder(); _messageBuffer.AppendLine(message); } /// <summary> /// Appends the trace information and message /// </summary> /// <param name="eventCache">the Event Cache</param> /// <param name="source">the Source</param> /// <param name="eventType">the Event Type</param> /// <param name="id">the Id</param> /// <param name="message">the Message</param> public override void TraceEvent(TraceEventCache eventCache, string source, TraceEventType eventType, int id, string message) { base.TraceEvent(eventCache, source, eventType, id, message); AppendEntry(id, eventType, eventCache); } /// <summary> /// Adds the trace information to a collection of LogEntry objects /// </summary> /// <param name="id">the Id</param> /// <param name="eventType">the Event Type</param> /// <param name="eventCache">the EventCache</param> private void AppendEntry(int id, TraceEventType eventType, TraceEventCache eventCache) { if (_messageBuffer == null) _messageBuffer = new StringBuilder(); var message = _messageBuffer.ToString(); _messageBuffer.Length = 0; if (message.EndsWith(Environment.NewLine)) message = message.Substring(0, message.Length - Environment.NewLine.Length); if (message.Length == 0) return; var entry = new LogEntry() { PartitionKey = string.Format("{0:D10}", eventCache.Timestamp >> 30), RowKey = string.Format("{0:D19}", eventCache.Timestamp), EventTickCount = eventCache.Timestamp, Level = (int)eventType, EventId = id, Pid = eventCache.ProcessId, Tid = eventCache.ThreadId, Message = message }; lock (_traceLogAccess) _traceLog.Add(entry); } #endregion #endregion } }

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• Capturing and Transforming ASP.NET Output with Response.Filter

  - by Rick Strahl

  During one of my Handlers and Modules session at DevConnections this week one of the attendees asked a question that I didn’t have an immediate answer for. Basically he wanted to capture response output completely and then apply some filtering to the output – effectively injecting some additional content into the page AFTER the page had completely rendered. Specifically the output should be captured from anywhere – not just a page and have this code injected into the page. Some time ago I posted some code that allows you to capture ASP.NET Page output by overriding the Render() method, capturing the HtmlTextWriter() and reading its content, modifying the rendered data as text then writing it back out. I’ve actually used this approach on a few occasions and it works fine for ASP.NET pages. But this obviously won’t work outside of the Page class environment and it’s not really generic – you have to create a custom page class in order to handle the output capture. [updated 11/16/2009 – updated ResponseFilterStream implementation and a few additional notes based on comments] Enter Response.Filter However, ASP.NET includes a Response.Filter which can be used – well to filter output. Basically Response.Filter is a stream through which the OutputStream is piped back to the Web Server (indirectly). As content is written into the Response object, the filter stream receives the appropriate Stream commands like Write, Flush and Close as well as read operations although for a Response.Filter that’s uncommon to be hit. The Response.Filter can be programmatically replaced at runtime which allows you to effectively intercept all output generation that runs through ASP.NET. A common Example: Dynamic GZip Encoding A rather common use of Response.Filter hooking up code based, dynamic  GZip compression for requests which is dead simple by applying a GZipStream (or DeflateStream) to Response.Filter. The following generic routines can be used very easily to detect GZip capability of the client and compress response output with a single line of code and a couple of library helper routines: WebUtils.GZipEncodePage(); which is handled with a few lines of reusable code and a couple of static helper methods: /// <summary> ///Sets up the current page or handler to use GZip through a Response.Filter ///IMPORTANT:  ///You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() {     HttpResponse Response = HttpContext.Current.Response;     if(IsGZipSupported())     {         stringAcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"];         if(AcceptEncoding.Contains("deflate"))         {             Response.Filter = newSystem.IO.Compression.DeflateStream(Response.Filter,                                        System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "deflate");         }         else        {             Response.Filter = newSystem.IO.Compression.GZipStream(Response.Filter,                                       System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "gzip");                            }     }     // Allow proxy servers to cache encoded and unencoded versions separately    Response.AppendHeader("Vary", "Content-Encoding"); } /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } GZipStream and DeflateStream are streams that are assigned to Response.Filter and by doing so apply the appropriate compression on the active Response. Response.Filter content is chunked So to implement a Response.Filter effectively requires only that you implement a custom stream and handle the Write() method to capture Response output as it’s written. At first blush this seems very simple – you capture the output in Write, transform it and write out the transformed content in one pass. And that indeed works for small amounts of content. But you see, the problem is that output is written in small buffer chunks (a little less than 16k it appears) rather than just a single Write() statement into the stream, which makes perfect sense for ASP.NET to stream data back to IIS in smaller chunks to minimize memory usage en route. Unfortunately this also makes it a more difficult to implement any filtering routines since you don’t directly get access to all of the response content which is problematic especially if those filtering routines require you to look at the ENTIRE response in order to transform or capture the output as is needed for the solution the gentleman in my session asked for. So in order to address this a slightly different approach is required that basically captures all the Write() buffers passed into a cached stream and then making the stream available only when it’s complete and ready to be flushed. As I was thinking about the implementation I also started thinking about the few instances when I’ve used Response.Filter implementations. Each time I had to create a new Stream subclass and create my custom functionality but in the end each implementation did the same thing – capturing output and transforming it. I thought there should be an easier way to do this by creating a re-usable Stream class that can handle stream transformations that are common to Response.Filter implementations. Creating a semi-generic Response Filter Stream Class What I ended up with is a ResponseFilterStream class that provides a handful of Events that allow you to capture and/or transform Response content. The class implements a subclass of Stream and then overrides Write() and Flush() to handle capturing and transformation operations. By exposing events it’s easy to hook up capture or transformation operations via single focused methods. ResponseFilterStream exposes the following events: CaptureStream, CaptureString Captures the output only and provides either a MemoryStream or String with the final page output. Capture is hooked to the Flush() operation of the stream. TransformStream, TransformString Allows you to transform the complete response output with events that receive a MemoryStream or String respectively and can you modify the output then return it back as a return value. The transformed output is then written back out in a single chunk to the response output stream. These events capture all output internally first then write the entire buffer into the response. TransformWrite, TransformWriteString Allows you to transform the Response data as it is written in its original chunk size in the Stream’s Write() method. Unlike TransformStream/TransformString which operate on the complete output, these events only see the current chunk of data written. This is more efficient as there’s no caching involved, but can cause problems due to searched content splitting over multiple chunks. Using this implementation, creating a custom Response.Filter transformation becomes as simple as the following code. To hook up the Response.Filter using the MemoryStream version event: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformStream += filter_TransformStream; Response.Filter = filter; and the event handler to do the transformation: MemoryStream filter_TransformStream(MemoryStream ms) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = encoding.GetString(ms.ToArray()); output = FixPaths(output); ms = new MemoryStream(output.Length); byte[] buffer = encoding.GetBytes(output); ms.Write(buffer,0,buffer.Length); return ms; } private string FixPaths(string output) { string path = HttpContext.Current.Request.ApplicationPath; // override root path wonkiness if (path == "/") path = ""; output = output.Replace("\"~/", "\"" + path + "/").Replace("'~/", "'" + path + "/"); return output; } The idea of the event handler is that you can do whatever you want to the stream and return back a stream – either the same one that’s been modified or a brand new one – which is then sent back to as the final response. The above code can be simplified even more by using the string version events which handle the stream to string conversions for you: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; and the event handler to do the transformation calling the same FixPaths method shown above: string filter_TransformString(string output) { return FixPaths(output); } The events for capturing output and capturing and transforming chunks work in a very similar way. By using events to handle the transformations ResponseFilterStream becomes a reusable component and we don’t have to create a new stream class or subclass an existing Stream based classed. By the way, the example used here is kind of a cool trick which transforms “~/” expressions inside of the final generated HTML output – even in plain HTML controls not HTML controls – and transforms them into the appropriate application relative path in the same way that ResolveUrl would do. So you can write plain old HTML like this: <a href=”~/default.aspx”>Home</a>  and have it turned into: <a href=”/myVirtual/default.aspx”>Home</a>  without having to use an ASP.NET control like Hyperlink or Image or having to constantly use: <img src=”<%= ResolveUrl(“~/images/home.gif”) %>” /> in MVC applications (which frankly is one of the most annoying things about MVC especially given the path hell that extension-less and endpoint-less URLs impose). I can’t take credit for this idea. While discussing the Response.Filter issues on Twitter a hint from Dylan Beattie who pointed me at one of his examples which does something similar. I thought the idea was cool enough to use an example for future demos of Response.Filter functionality in ASP.NET next I time I do the Modules and Handlers talk (which was great fun BTW). How practical this is is debatable however since there’s definitely some overhead to using a Response.Filter in general and especially on one that caches the output and the re-writes it later. Make sure to test for performance anytime you use Response.Filter hookup and make sure it' doesn’t end up killing perf on you. You’ve been warned :-}. How does ResponseFilterStream work? The big win of this implementation IMHO is that it’s a reusable  component – so for implementation there’s no new class, no subclassing – you simply attach to an event to implement an event handler method with a straight forward signature to retrieve the stream or string you’re interested in. The implementation is based on a subclass of Stream as is required in order to handle the Response.Filter requirements. What’s different than other implementations I’ve seen in various places is that it supports capturing output as a whole to allow retrieving the full response output for capture or modification. The exception are the TransformWrite and TransformWrite events which operate only active chunk of data written by the Response. For captured output, the Write() method captures output into an internal MemoryStream that is cached until writing is complete. So Write() is called when ASP.NET writes to the Response stream, but the filter doesn’t pass on the Write immediately to the filter’s internal stream. The data is cached and only when the Flush() method is called to finalize the Stream’s output do we actually send the cached stream off for transformation (if the events are hooked up) and THEN finally write out the returned content in one big chunk. Here’s the implementation of ResponseFilterStream: /// <summary> /// A semi-generic Stream implementation for Response.Filter with /// an event interface for handling Content transformations via /// Stream or String. /// <remarks> /// Use with care for large output as this implementation copies /// the output into a memory stream and so increases memory usage. /// </remarks> /// </summary> public class ResponseFilterStream : Stream { /// <summary> /// The original stream /// </summary> Stream _stream; /// <summary> /// Current position in the original stream /// </summary> long _position; /// <summary> /// Stream that original content is read into /// and then passed to TransformStream function /// </summary> MemoryStream _cacheStream = new MemoryStream(5000); /// <summary> /// Internal pointer that that keeps track of the size /// of the cacheStream /// </summary> int _cachePointer = 0; /// <summary> /// /// </summary> /// <param name="responseStream"></param> public ResponseFilterStream(Stream responseStream) { _stream = responseStream; } /// <summary> /// Determines whether the stream is captured /// </summary> private bool IsCaptured { get { if (CaptureStream != null || CaptureString != null || TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Determines whether the Write method is outputting data immediately /// or delaying output until Flush() is fired. /// </summary> private bool IsOutputDelayed { get { if (TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Event that captures Response output and makes it available /// as a MemoryStream instance. Output is captured but won't /// affect Response output. /// </summary> public event Action<MemoryStream> CaptureStream; /// <summary> /// Event that captures Response output and makes it available /// as a string. Output is captured but won't affect Response output. /// </summary> public event Action<string> CaptureString; /// <summary> /// Event that allows you transform the stream as each chunk of /// the output is written in the Write() operation of the stream. /// This means that that it's possible/likely that the input /// buffer will not contain the full response output but only /// one of potentially many chunks. /// /// This event is called as part of the filter stream's Write() /// operation. /// </summary> public event Func<byte[], byte[]> TransformWrite; /// <summary> /// Event that allows you to transform the response stream as /// each chunk of bytep[] output is written during the stream's write /// operation. This means it's possibly/likely that the string /// passed to the handler only contains a portion of the full /// output. Typical buffer chunks are around 16k a piece. /// /// This event is called as part of the stream's Write operation. /// </summary> public event Func<string, string> TransformWriteString; /// <summary> /// This event allows capturing and transformation of the entire /// output stream by caching all write operations and delaying final /// response output until Flush() is called on the stream. /// </summary> public event Func<MemoryStream, MemoryStream> TransformStream; /// <summary> /// Event that can be hooked up to handle Response.Filter /// Transformation. Passed a string that you can modify and /// return back as a return value. The modified content /// will become the final output. /// </summary> public event Func<string, string> TransformString; protected virtual void OnCaptureStream(MemoryStream ms) { if (CaptureStream != null) CaptureStream(ms); } private void OnCaptureStringInternal(MemoryStream ms) { if (CaptureString != null) { string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); OnCaptureString(content); } } protected virtual void OnCaptureString(string output) { if (CaptureString != null) CaptureString(output); } protected virtual byte[] OnTransformWrite(byte[] buffer) { if (TransformWrite != null) return TransformWrite(buffer); return buffer; } private byte[] OnTransformWriteStringInternal(byte[] buffer) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = OnTransformWriteString(encoding.GetString(buffer)); return encoding.GetBytes(output); } private string OnTransformWriteString(string value) { if (TransformWriteString != null) return TransformWriteString(value); return value; } protected virtual MemoryStream OnTransformCompleteStream(MemoryStream ms) { if (TransformStream != null) return TransformStream(ms); return ms; } /// <summary> /// Allows transforming of strings /// /// Note this handler is internal and not meant to be overridden /// as the TransformString Event has to be hooked up in order /// for this handler to even fire to avoid the overhead of string /// conversion on every pass through. /// </summary> /// <param name="responseText"></param> /// <returns></returns> private string OnTransformCompleteString(string responseText) { if (TransformString != null) TransformString(responseText); return responseText; } /// <summary> /// Wrapper method form OnTransformString that handles /// stream to string and vice versa conversions /// </summary> /// <param name="ms"></param> /// <returns></returns> internal MemoryStream OnTransformCompleteStringInternal(MemoryStream ms) { if (TransformString == null) return ms; //string content = ms.GetAsString(); string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); content = TransformString(content); byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(content); ms = new MemoryStream(); ms.Write(buffer, 0, buffer.Length); //ms.WriteString(content); return ms; } /// <summary> /// /// </summary> public override bool CanRead { get { return true; } } public override bool CanSeek { get { return true; } } /// <summary> /// /// </summary> public override bool CanWrite { get { return true; } } /// <summary> /// /// </summary> public override long Length { get { return 0; } } /// <summary> /// /// </summary> public override long Position { get { return _position; } set { _position = value; } } /// <summary> /// /// </summary> /// <param name="offset"></param> /// <param name="direction"></param> /// <returns></returns> public override long Seek(long offset, System.IO.SeekOrigin direction) { return _stream.Seek(offset, direction); } /// <summary> /// /// </summary> /// <param name="length"></param> public override void SetLength(long length) { _stream.SetLength(length); } /// <summary> /// /// </summary> public override void Close() { _stream.Close(); } /// <summary> /// Override flush by writing out the cached stream data /// </summary> public override void Flush() { if (IsCaptured && _cacheStream.Length > 0) { // Check for transform implementations _cacheStream = OnTransformCompleteStream(_cacheStream); _cacheStream = OnTransformCompleteStringInternal(_cacheStream); OnCaptureStream(_cacheStream); OnCaptureStringInternal(_cacheStream); // write the stream back out if output was delayed if (IsOutputDelayed) _stream.Write(_cacheStream.ToArray(), 0, (int)_cacheStream.Length); // Clear the cache once we've written it out _cacheStream.SetLength(0); } // default flush behavior _stream.Flush(); } /// <summary> /// /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> /// <returns></returns> public override int Read(byte[] buffer, int offset, int count) { return _stream.Read(buffer, offset, count); } /// <summary> /// Overriden to capture output written by ASP.NET and captured /// into a cached stream that is written out later when Flush() /// is called. /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> public override void Write(byte[] buffer, int offset, int count) { if ( IsCaptured ) { // copy to holding buffer only - we'll write out later _cacheStream.Write(buffer, 0, count); _cachePointer += count; } // just transform this buffer if (TransformWrite != null) buffer = OnTransformWrite(buffer); if (TransformWriteString != null) buffer = OnTransformWriteStringInternal(buffer); if (!IsOutputDelayed) _stream.Write(buffer, offset, buffer.Length); } } The key features are the events and corresponding OnXXX methods that handle the event hookups, and the Write() and Flush() methods of the stream implementation. All the rest of the members tend to be plain jane passthrough stream implementation code without much consequence. I do love the way Action<t> and Func<T> make it so easy to create the event signatures for the various events – sweet. A few Things to consider Performance Response.Filter is not great for performance in general as it adds another layer of indirection to the ASP.NET output pipeline, and this implementation in particular adds a memory hit as it basically duplicates the response output into the cached memory stream which is necessary since you may have to look at the entire response. If you have large pages in particular this can cause potentially serious memory pressure in your server application. So be careful of wholesale adoption of this (or other) Response.Filters. Make sure to do some performance testing to ensure it’s not killing your app’s performance. Response.Filter works everywhere A few questions came up in comments and discussion as to capturing ALL output hitting the site and – yes you can definitely do that by assigning a Response.Filter inside of a module. If you do this however you’ll want to be very careful and decide which content you actually want to capture especially in IIS 7 which passes ALL content – including static images/CSS etc. through the ASP.NET pipeline. So it is important to filter only on what you’re looking for – like the page extension or maybe more effectively the Response.ContentType. Response.Filter Chaining Originally I thought that filter chaining doesn’t work at all due to a bug in the stream implementation code. But it’s quite possible to assign multiple filters to the Response.Filter property. So the following actually works to both compress the output and apply the transformed content: WebUtils.GZipEncodePage(); ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; However the following does not work resulting in invalid content encoding errors: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; WebUtils.GZipEncodePage(); In other words multiple Response filters can work together but it depends entirely on the implementation whether they can be chained or in which order they can be chained. In this case running the GZip/Deflate stream filters apparently relies on the original content length of the output and chokes when the content is modified. But if attaching the compression first it works fine as unintuitive as that may seem. Resources Download example code Capture Output from ASP.NET Pages © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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• SQL SERVER – Introduction to Extended Events – Finding Long Running Queries

  - by pinaldave

  The job of an SQL Consultant is very interesting as always. The month before, I was busy doing query optimization and performance tuning projects for our clients, and this month, I am busy delivering my performance in Microsoft SQL Server 2005/2008 Query Optimization and & Performance Tuning Course. I recently read white paper about Extended Event by SQL Server MVP Jonathan Kehayias. You can read the white paper here: Using SQL Server 2008 Extended Events. I also read another appealing chapter by Jonathan in the book, SQLAuthority Book Review – Professional SQL Server 2008 Internals and Troubleshooting. After reading these excellent notes by Jonathan, I decided to upgrade my course and include Extended Event as one of the modules. This week, I have delivered Extended Events session two times and attendees really liked the said course. They really think Extended Events is one of the most powerful tools available. Extended Events can do many things. I suggest that you read the white paper I mentioned to learn more about this tool. Instead of writing a long theory, I am going to write a very quick script for Extended Events. This event session captures all the longest running queries ever since the event session was started. One of the many advantages of the Extended Events is that it can be configured very easily and it is a robust method to collect necessary information in terms of troubleshooting. There are many targets where you can store the information, which include XML file target, which I really like. In the following Events, we are writing the details of the event at two locations: 1) Ringer Buffer; and 2) XML file. It is not necessary to write at both places, either of the two will do. -- Extended Event for finding *long running query* IF EXISTS(SELECT * FROM sys.server_event_sessions WHERE name='LongRunningQuery') DROP EVENT SESSION LongRunningQuery ON SERVER GO -- Create Event CREATE EVENT SESSION LongRunningQuery ON SERVER -- Add event to capture event ADD EVENT sqlserver.sql_statement_completed ( -- Add action - event property ACTION (sqlserver.sql_text, sqlserver.tsql_stack) -- Predicate - time 1000 milisecond WHERE sqlserver.sql_statement_completed.duration > 1000 ) -- Add target for capturing the data - XML File ADD TARGET package0.asynchronous_file_target( SET filename='c:\LongRunningQuery.xet', metadatafile='c:\LongRunningQuery.xem'), -- Add target for capturing the data - Ring Bugger ADD TARGET package0.ring_buffer (SET max_memory = 4096) WITH (max_dispatch_latency = 1 seconds) GO -- Enable Event ALTER EVENT SESSION LongRunningQuery ON SERVER STATE=START GO -- Run long query (longer than 1000 ms) SELECT * FROM AdventureWorks.Sales.SalesOrderDetail ORDER BY UnitPriceDiscount DESC GO -- Stop the event ALTER EVENT SESSION LongRunningQuery ON SERVER STATE=STOP GO -- Read the data from Ring Buffer SELECT CAST(dt.target_data AS XML) AS xmlLockData FROM sys.dm_xe_session_targets dt JOIN sys.dm_xe_sessions ds ON ds.Address = dt.event_session_address JOIN sys.server_event_sessions ss ON ds.Name = ss.Name WHERE dt.target_name = 'ring_buffer' AND ds.Name = 'LongRunningQuery' GO -- Read the data from XML File SELECT event_data_XML.value('(event/data[1])[1]','VARCHAR(100)') AS Database_ID, event_data_XML.value('(event/data[2])[1]','INT') AS OBJECT_ID, event_data_XML.value('(event/data[3])[1]','INT') AS object_type, event_data_XML.value('(event/data[4])[1]','INT') AS cpu, event_data_XML.value('(event/data[5])[1]','INT') AS duration, event_data_XML.value('(event/data[6])[1]','INT') AS reads, event_data_XML.value('(event/data[7])[1]','INT') AS writes, event_data_XML.value('(event/action[1])[1]','VARCHAR(512)') AS sql_text, event_data_XML.value('(event/action[2])[1]','VARCHAR(512)') AS tsql_stack, CAST(event_data_XML.value('(event/action[2])[1]','VARCHAR(512)') AS XML).value('(frame/@handle)[1]','VARCHAR(50)') AS handle FROM ( SELECT CAST(event_data AS XML) event_data_XML, * FROM sys.fn_xe_file_target_read_file ('c:\LongRunningQuery*.xet', 'c:\LongRunningQuery*.xem', NULL, NULL)) T GO -- Clean up. Drop the event DROP EVENT SESSION LongRunningQuery ON SERVER GO Just run the above query, afterwards you will find following result set. This result set contains the query that was running over 1000 ms. In our example, I used the XML file, and it does not reset when SQL services or computers restarts (if you are using DMV, it will reset when SQL services restarts). This event session can be very helpful for troubleshooting. Let me know if you want me to write more about Extended Events. I am totally fascinated with this feature, so I’m planning to acquire more knowledge about it so I can determine its other usages. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Training, SQLServer, T SQL, Technology Tagged: SQL Extended Events

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• Install Quartz.Net as a windows service and Test installation

  - by Tarun Arora

  In this blog post I’ll be covering, 01: Where to download Quartz.net from 02: How to install Quartz.net as a Windows service 03: Test the Quartz.net Installation If you are new to Quartz.net I would recommend reading the blog post on a brief introduction to Quartz.net. 01 – Where to download Quartz.net? http://sourceforge.net/projects/quartznet/files/quartznet/       Currently version  Quartz.Net 2.0.1 is the recommended download version. 02 – How to install Quartz.net as a Windows service         Go to the download location and unzip the Quartz.net package Navigate to the folder Quartz.Net \ Server \ bin – This is where you will find different .net version installers of the quartz.net packages. For example in the screen shot above, you can see the Quartz.net .net 3.5 and .net 4 packages. Open up the Quartz.net .net 4.0 folder, this folder contains the files you need to install Quartz.net as a windows service Copy the contents of the folder Downloads\Quartz.NET-2.0.1\server\bin\4.0 to the folder %program files%\Quartz.net   5. Open up a new CMD as an administrator and run the below command to install Quartz.net as a windows service /> Quartz.Server.exe install 6. How do I know that Quartz.Net service has installed as a Windows service? Go to run prompt and type ‘services.msc’ you should now see all the windows services installed on your machine. Navigate down to look for Quartz.Net. The service installs itself as an automatic startup Type and log on as ‘Local System’. You can easily change this to your prefer account that you would like to run the service as. If you wanted to name the Quartz service something else then that’s also possible… Can I change the default display name of the quartz.net windows service? Yes, you can! Navigate to C:\Program Files (x86)\Quartz.Net\ and open up the config file ‘quartz.config’ - You can change the instance name - You can change the default thread count of 10 - The port that the service listens to (by default this is port 555) A blog post on more configuration details can be found here. 03 – Test Quartz.Net windows service installation So, I have installed Quartz.Net as a windows service, how do I test whether my installation has been successful. Open up cmd as an administrator and run the below command, C:\Program Files (x86)\Quartz.Net> Quartz.Server.exe –i Since by default the Quartz.net windows service writes INFO level diagnostics (this can be changed from Quartz.Server.exe.config) you should see the service information show up on the console. For instance in the example above I can see that the service is running in a NON CLUSTERED mode, its currently not started and is currently in standby mode with 0 number of jobs executed so far… This was second in the series of posts on enterprise scheduling using Quartz.net, in the next post I’ll be covering how to run your first scheduled task using Quartz.net windows service. Thank you for taking the time out and reading this blog post. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Stay tuned!

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• SQLAuthority News – Guest Post – Performance Counters Gathering using Powershell

  - by pinaldave

  Laerte Junior Laerte Junior has previously helped me personally to resolve the issue with Powershell installation on my computer. He did awesome job to help. He has send this another wonderful article regarding performance counter for readers of this blog. I really liked it and I expect all of you who are Powershell geeks, you will like the same as well. As a good DBA, you know that our social life is restricted to a few movies over the year and, when possible, a pizza in a restaurant next to your company’s place, of course. So what we have to do is to create methods through which we can facilitate our daily processes to go home early, and eventually have a nice time with our family (and not sleeping on the couch). As a consultant or fixed employee, one of our daily tasks is to monitor performance counters using Perfmom. To be honest, IDE is getting more complicated. To deal with this, I thought a solution using Powershell. Yes, with some lines of Powershell, you can configure which counters to use. And with one more line, you can already start collecting data. Let’s see one scenario: You are a consultant who has several clients and has just closed another project in troubleshooting an SQL Server environment. You are to use Perfmom to collect data from the server and you already have its XML configuration files made with the counters that you will be using- a file for memory bottleneck f, one for CPU, etc. With one Powershell command line for each XML file, you start collecting. The output of such a TXT file collection is set to up in an SQL Server. With two lines of command for each XML, you make the whole process of data collection. Creating an XML configuration File to Memory Counters: Get-PerfCounterCategory -CategoryName "Memory" | Get-PerfCounterInstance  | Get-PerfCounterCounters |Save-ConfigPerfCounter -PathConfigFile "c:\temp\ConfigfileMemory.xml" -newfile Creating an XML Configuration File to Buffer Manager, counters Page lookups/sec, Page reads/sec, Page writes/sec, Page life expectancy: Get-PerfCounterCategory -CategoryName "SQLServer:Buffer Manager" | Get-PerfCounterInstance | Get-PerfCounterCounters -CounterName "Page*" | Save-ConfigPerfCounter -PathConfigFile "c:\temp\BufferManager.xml" –NewFile Then you start the collection: Set-CollectPerfCounter -DateTimeStart "05/24/2010 08:00:00" -DateTimeEnd "05/24/2010 22:00:00" -Interval 10 -PathConfigFile c:\temp\ConfigfileMemory.xml -PathOutputFile c:\temp\ConfigfileMemory.txt To let the Buffer Manager collect, you need one more counters, including the Buffer cache hit ratio. Just add a new counter to BufferManager.xml, omitting the new file parameter Get-PerfCounterCategory -CategoryName "SQLServer:Buffer Manager" | Get-PerfCounterInstance | Get-PerfCounterCounters -CounterName "Buffer cache hit ratio" | Save-ConfigPerfCounter -PathConfigFile "c:\temp\BufferManager.xml" And start the collection: Set-CollectPerfCounter -DateTimeStart "05/24/2010 08:00:00" -DateTimeEnd "05/24/2010 22:00:00" -Interval 10 -PathConfigFile c:\temp\BufferManager.xml -PathOutputFile c:\temp\BufferManager.txt You do not know which counters are in the Category Buffer Manager? Simple! Get-PerfCounterCategory -CategoryName "SQLServer:Buffer Manager" | Get-PerfCounterInstance | Get-PerfCounterCounters Let’s see one output file as shown below. It is ready to bulk insert into the SQL Server. As you can see, Powershell makes this process incredibly easy and fast. Do you want to see more examples? Visit my blog at Shell Your Experience You can find more about Laerte Junior over here: www.laertejuniordba.spaces.live.com www.simple-talk.com/author/laerte-junior www.twitter.com/laertejuniordba SQL Server Powershell Extension Team: http://sqlpsx.codeplex.com/ Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: SQL, SQL Add-On, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology Tagged: Powershell

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• Write, Read and Update Oracle CLOBs with PL/SQL

  - by robertphyatt

  Fun with CLOBS! If you are using Oracle, if you have to deal with text that is over 4000 bytes, you will probably find yourself dealing with CLOBs, which can go up to 4GB. They are pretty tricky, and it took me a long time to figure out these lessons learned. I hope they will help some down-trodden developer out there somehow. Here is my original code, which worked great on my Oracle Express Edition: (for all examples, the first one writes a new CLOB, the next one Updates an existing CLOB and the final one reads a CLOB back) CREATE OR REPLACE PROCEDURE PRC_WR_CLOB (        p_document      IN VARCHAR2,        p_id            OUT NUMBER) IS      lob_loc CLOB; BEGIN    INSERT INTO TBL_CLOBHOLDERDDOC (CLOBHOLDERDDOC)        VALUES (empty_CLOB())        RETURNING CLOBHOLDERDDOC, CLOBHOLDERDDOCID INTO lob_loc, p_id;    DBMS_LOB.WRITE(lob_loc, LENGTH(UTL_RAW.CAST_TO_RAW(p_document)), 1, UTL_RAW.CAST_TO_RAW(p_document)); END; / CREATE OR REPLACE PROCEDURE PRC_UD_CLOB (        p_document      IN VARCHAR2,        p_id            IN NUMBER) IS      lob_loc CLOB; BEGIN        SELECT CLOBHOLDERDDOC INTO lob_loc FROM TBL_CLOBHOLDERDDOC        WHERE CLOBHOLDERDDOCID = p_id FOR UPDATE;    DBMS_LOB.WRITE(lob_loc, LENGTH(UTL_RAW.CAST_TO_RAW(p_document)), 1, UTL_RAW.CAST_TO_RAW(p_document)); END; / CREATE OR REPLACE PROCEDURE PRC_RD_CLOB (    p_id IN NUMBER,    p_clob OUT VARCHAR2) IS    lob_loc  CLOB; BEGIN    SELECT CLOBHOLDERDDOC INTO lob_loc    FROM   TBL_CLOBHOLDERDDOC    WHERE  CLOBHOLDERDDOCID = p_id;    p_clob := UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(lob_loc, DBMS_LOB.GETLENGTH(lob_loc), 1)); END; / As you can see, I had originally been casting everything back and forth between RAW formats using the UTL_RAW.CAST_TO_VARCHAR2() and UTL_RAW.CAST_TO_RAW() functions all over the place, but it had the nasty side effect of working great on my Oracle express edition on my developer box, but having all the CLOBs above a certain size display garbage when read back on the Oracle test database server . So...I kept working at it and came up with the following, which ALSO worked on my Oracle Express Edition on my developer box:   CREATE OR REPLACE PROCEDURE PRC_WR_CLOB (     p_document      IN VARCHAR2,     p_id        OUT NUMBER) IS       lob_loc CLOB; BEGIN     INSERT INTO TBL_CLOBHOLDERDOC (CLOBHOLDERDOC)         VALUES (empty_CLOB())         RETURNING CLOBHOLDERDOC, CLOBHOLDERDOCID INTO lob_loc, p_id;     DBMS_LOB.WRITE(lob_loc, LENGTH(p_document), 1, p_document);   END; / CREATE OR REPLACE PROCEDURE PRC_UD_CLOB (     p_document      IN VARCHAR2,     p_id        IN NUMBER) IS       lob_loc CLOB; BEGIN     SELECT CLOBHOLDERDOC INTO lob_loc FROM TBL_CLOBHOLDERDOC     WHERE CLOBHOLDERDOCID = p_id FOR UPDATE;     DBMS_LOB.WRITE(lob_loc, LENGTH(p_document), 1, p_document); END; / CREATE OR REPLACE PROCEDURE PRC_RD_CLOB (     p_id IN NUMBER,     p_clob OUT VARCHAR2) IS     lob_loc  CLOB; BEGIN     SELECT CLOBHOLDERDOC INTO lob_loc     FROM   TBL_CLOBHOLDERDOC     WHERE  CLOBHOLDERDOCID = p_id;     p_clob := DBMS_LOB.SUBSTR(lob_loc, DBMS_LOB.GETLENGTH(lob_loc), 1); END; / Unfortunately, by changing my code to what you see above, even though it kept working on my Oracle express edition, everything over a certain size just started truncating after about 7950 characters on the test server! Here is what I came up with in the end, which is actually the simplest solution and this time worked on both my express edition and on the database server (note that only the read function was changed to fix the truncation issue, and that I had Oracle worry about converting the CLOB into a VARCHAR2 internally): CREATE OR REPLACE PROCEDURE PRC_WR_CLOB (        p_document      IN VARCHAR2,        p_id            OUT NUMBER) IS      lob_loc CLOB; BEGIN    INSERT INTO TBL_CLOBHOLDERDDOC (CLOBHOLDERDDOC)        VALUES (empty_CLOB())        RETURNING CLOBHOLDERDDOC, CLOBHOLDERDDOCID INTO lob_loc, p_id;    DBMS_LOB.WRITE(lob_loc, LENGTH(p_document), 1, p_document); END; / CREATE OR REPLACE PROCEDURE PRC_UD_CLOB (        p_document      IN VARCHAR2,        p_id            IN NUMBER) IS      lob_loc CLOB; BEGIN        SELECT CLOBHOLDERDDOC INTO lob_loc FROM TBL_CLOBHOLDERDDOC        WHERE CLOBHOLDERDDOCID = p_id FOR UPDATE;    DBMS_LOB.WRITE(lob_loc, LENGTH(p_document), 1, p_document); END; / CREATE OR REPLACE PROCEDURE PRC_RD_CLOB (    p_id IN NUMBER,    p_clob OUT VARCHAR2) IS BEGIN    SELECT CLOBHOLDERDDOC INTO p_clob    FROM   TBL_CLOBHOLDERDDOC    WHERE  CLOBHOLDERDDOCID = p_id; END; /   I hope that is useful to someone!

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• Oracle Support Master Note for Troubleshooting Advanced Queuing and Oracle Streams Propagation Issues (Doc ID 233099.1)

  - by faye.todd(at)oracle.com

  Master Note for Troubleshooting Advanced Queuing and Oracle Streams Propagation Issues (Doc ID 233099.1) Copyright (c) 2010, Oracle Corporation. All Rights Reserved. In this Document  Purpose  Last Review Date  Instructions for the Reader  Troubleshooting Details     1. Scope and Application      2. Definitions and Classifications     3. How to Use This Guide     4. Basic AQ Propagation Troubleshooting     5. Additional Troubleshooting Steps for AQ Propagation of User-Enqueued and Dequeued Messages     6. Additional Troubleshooting Steps for Propagation in an Oracle Streams Environment     7. Performance Issues  References Applies to: Oracle Server - Enterprise Edition - Version: 8.1.7.0 to 11.2.0.2 - Release: 8.1.7 to 11.2Information in this document applies to any platform. Purpose This document presents a step-by-step methodology for troubleshooting and resolving problems with Advanced Queuing Propagation in both Streams and basic Advanced Queuing environments. It also serves as a master reference for other more specific notes on Oracle Streams Propagation and Advanced Queuing Propagation issues. Last Review Date December 20, 2010 Instructions for the Reader A Troubleshooting Guide is provided to assist in debugging a specific issue. When possible, diagnostic tools are included in the document to assist in troubleshooting. Troubleshooting Details 1. Scope and Application This note is intended for Database Administrators of Oracle databases where issues are being encountered with propagating messages between advanced queues, whether the queues are used for user-created messaging systems or for Oracle Streams. It contains troubleshooting steps and links to notes for further problem resolution.It can also be used a template to document a problem when it is necessary to engage Oracle Support Services. Knowing what is NOT happening can frequently speed up the resolution process by focusing solely on the pertinent problem area. This guide is divided into five parts: Section 2: Definitions and Classifications (discusses the different types and features of propagations possible - helpful for understanding the rest of the guide) Section 3: How to Use this Guide (to be used as a start part for determining the scope of the problem and what sections to consult) Section 4. Basic AQ propagation troubleshooting (applies to both AQ propagation of user enqueued and dequeued messages as well as Oracle Streams propagations) Section 5. Additional troubleshooting steps for AQ propagation of user enqueued and dequeued messages Section 6. Additional troubleshooting steps for Oracle Streams propagation Section 7. Performance issues 2. Definitions and Classifications Given the potential scope of issues that can be encountered with AQ propagation, the first recommended step is to do some basic diagnosis to determine the type of problem that is being encountered. 2.1. What Type of Propagation is Being Used? 2.1.1. Buffered Messaging For an advanced queue, messages can be maintained on disk (persistent messaging) or in memory (buffered messaging). To determine if a queue is buffered or not, reference the GV_$BUFFERED_QUEUES view. If the queue does not appear in this view, it is persistent. 2.1.2. Propagation mode - queue-to-dblink vs queue-to-queue As of 10.2, an AQ propagation can also be defined as queue-to-dblink, or queue-to-queue: queue-to-dblink: The propagation delivers messages or events from the source queue to all subscribing queues at the destination database identified by the dblink. A single propagation schedule is used to propagate messages to all subscribing queues. Hence any changes made to this schedule will affect message delivery to all the subscribing queues. This mode does not support multiple propagations from the same source queue to the same target database. queue-to-queue: Added in 10.2, this propagation mode delivers messages or events from the source queue to a specific destination queue identified on the database link. This allows the user to have fine-grained control on the propagation schedule for message delivery. This new propagation mode also supports transparent failover when propagating to a destination Oracle RAC system. With queue-to-queue propagation, you are no longer required to re-point a database link if the owner instance of the queue fails on Oracle RAC. This mode supports multiple propagations to the same target database if the target queues are different. The default is queue-to-dblink. To verify if queue-to-queue propagation is being used, in non-Streams environments query DBA_QUEUE_SCHEDULES.DESTINATION - if a remote queue is listed along with the remote database link, then queue-to-queue propagation is being used. For Streams environments, the DBA_PROPAGATION.QUEUE_TO_QUEUE column can be checked.See the following note for a method to switch between the two modes:Document 827473.1 How to alter propagation from queue-to-queue to queue-to-dblink 2.1.3. Combined Capture and Apply (CCA) for Streams In 11g Oracle Streams environments, an optimization called Combined Capture and Apply (CCA) is implemented by default when possible. Although a propagation is configured in this case, Streams does not use it; instead it passes information directly from capture to an apply receiver. To see if CCA is in use: COLUMN CAPTURE_NAME HEADING 'Capture Name' FORMAT A30COLUMN OPTIMIZATION HEADING 'CCA Mode?' FORMAT A10SELECT CAPTURE_NAME, DECODE(OPTIMIZATION,0, 'No','Yes') OPTIMIZATIONFROM V$STREAMS_CAPTURE; Also, see the following note:Document 463820.1 Streams Combined Capture and Apply in 11g 2.2. Queue Table Compatibility There are three types of queue table compatibility. In more recent databases, queue tables may be present in all three modes of compatibility: 8.0 - earliest version, deprecated in 10.2 onwards 8.1 - support added for RAC, asynchronous notification, secure queues, queue level access control, rule-based subscribers, separate storage of history information 10.0 - if the database is in 10.1-compatible mode, then the default value for queue table compatibility is 10.0 2.3. Single vs Multiple Consumer Queue Tables If more than one recipient can dequeue a message from a queue, then its queue table is multiple consumer. You can propagate messages from a multiple-consumer queue to a single-consumer queue. Propagation from a single-consumer queue to a multiple-consumer queue is not possible. 3. How to Use This Guide 3.1. Are Messages Being Propagated at All, or is the Propagation Just Slow? Run the following query on the source database for the propagation (assuming that it is running): select TOTAL_NUMBER from DBA_QUEUE_SCHEDULES where QNAME='<source_queue_name>'; If TOTAL_NUMBER is increasing, then propagation is most likely functioning, although it may be slow. For performance issues, see Section 7. 3.2. Propagation Between Persistent User-Created Queues See Sections 4 and 5 (and optionally Section 6 if performance is an issue). 3.3. Propagation Between Buffered User-Created Queues See Sections 4, 5, and 6 (and optionally Section 7 if performance is an issue). 3.4. Propagation between Oracle Streams Queues (without Combined Capture and Apply (CCA) Optimization) See Sections 4 and 6 (and optionally Section 7 if performance is an issue). 3.5. Propagation between Oracle Streams Queues (with Combined Capture and Apply (CCA) Optimization) Although an AQ propagation is not used directly in this case, some characteristics of the message transfer are inferred from the propagation parameters used. Some parts of Sections 4 and 6 still apply. 3.6. Messaging Gateway Propagations This note does not apply to Messaging Gateway propagations. 4. Basic AQ Propagation Troubleshooting 4.1. Double-check Your Code Make sure that you are consistent in your usage of the database link(s) names, queue names, etc. It may be useful to plot a diagram of which queues are connected via which database links to make sure that the logical structure is correct. 4.2. Verify that Job Queue Processes are Running 4.2.1. Versions 10.2 and Lower - DBA_JOBS Package For versions 10.2 and lower, a scheduled propagation is managed by DBMS_JOB package. The propagation is performed by job queue process background processes. Therefore we need to verify that there are sufficient processes available for the propagation process. We should have at least 4 job queue processes running and preferably more depending on the number of other jobs running in the database. It should be noted that for AQ specific work, AQ will only ever use half of the job queue processes available.An issue caused by an inadequate job queue processes parameter setting is described in the following note:Document 298015.1 Kwqjswproc:Excep After Loop: Assigning To Self 4.2.1.1. Job Queue Processes in Initalization Parameter File The parameter JOB_QUEUE_PROCESSES in the init.ora/spfile should be > 0. The value can be changed dynamically via connect / as sysdbaalter system set JOB_QUEUE_PROCESSES=10; 4.2.1.2. Job Queue Processes in Memory The following command will show how many job queue processes are currentlyin use by this instance (this may be different than what is in the init.ora/spfile): connect / as sysdbashow parameter job; 4.2.1.3. OS PIDs Corresponding to Job Queue Processes Identify the operating system process ids (spids) of job queue processes involved in propagation via select p.SPID, p.PROGRAM from V$PROCESS p, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j where s.SID=jr.SID and s.PADDR=p.ADDR and jr.JOB=j.JOBand j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%'; and these SPIDs can be used to check at the operating system level that they exist.In 8i a job queue process will have a name similar to: ora_snp1_<instance_name>.In 9i onwards you will see a coordinator process: ora_cjq0_ and multiple slave processes: ora_jnnn_<instance_name>, where nnn is an integer between 1 and 999. 4.2.2. Version 11.1 and Above - Oracle Scheduler In version 11.1 and above, Oracle Scheduler is used to perform AQ and Streams propagations. Oracle Scheduler automatically tunes the number of slave processes for these jobs based on the load on the computer system, and the JOB_QUEUE_PROCESSES initialization parameter is only used to specify the maximum number of slave processes. Therefore, the JOB_QUEUE_PROCESSES initialization parameter does not need to be set (it defaults to a very high number), unless you want to limit the number of slaves that can be created. If JOB_QUEUE_PROCESSES = 0, no propagation jobs will run.See the following note for a discussion of Oracle Streams 11g and Oracle Scheduler:Document 1083608.1 11g Streams and Oracle Scheduler 4.2.2.1. Job Queue Processes in Initalization Parameter File The parameter JOB_QUEUE_PROCESSES in the init.ora/spfile should be > 0, and preferably be left at its default value. The value can be changed dynamically via connect / as sysdbaalter system set JOB_QUEUE_PROCESSES=10; To set the JOB_QUEUE_PROCESSES parameter to its default value, run: connect / as sysdbaalter system reset JOB_QUEUE_PROCESSES; and then bounce the instance. 4.2.2.2. Job Queue Processes in Memory The following command will show how many job queue processes are currently in use by this instance (this may be different than what is in the init.ora/spfile): connect / as sysdbashow parameter job; 4.2.2.3. OS PIDs Corresponding to Job Queue Processes Identify the operating system process ids (SPIDs) of job queue processes involved in propagation via col PROGRAM for a30select p.SPID, p.PROGRAM, j.JOB_namefrom v$PROCESS p, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j where s.SID=jr.SESSION_ID and s.PADDR=p.ADDRand jr.JOB_name=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%'; and these SPIDs can be used to check at the operating system level that they exist.You will see a coordinator process: ora_cjq0_ and multiple slave processes: ora_jnnn_<instance_name>, where nnn is an integer between 1 and 999. 4.3. Check the Alert Log and Any Associated Trace Files The first place to check for propagation failures is the alert logs at all sites (local and if relevant all remote sites). When a job queue process attempts to execute a schedule and fails it will always write an error stack to the alert log. This error stack will also be written in a job queue process trace file, which will be written to the BACKGROUND_DUMP_DEST location for 10.2 and below, and in the DIAGNOSTIC_DEST location for 11g. The fact that errors are written to the alert log demonstrates that the schedule is executing. This means that the problem could be with the set up of the schedule. In this example the ORA-02068 demonstrates that the failure was at the remote site. Further investigation revealed that the remote database was not open, hence the ORA-03114 error. Starting the database resolved the problem. Thu Feb 14 10:40:05 2002 Propagation Schedule for (AQADM.MULTIPLEQ, SHANE816.WORLD) encountered following error:ORA-04052: error occurred when looking up Remote object [email protected]: error occurred at recursive SQL level 4ORA-02068: following severe error from SHANE816ORA-03114: not connected to ORACLEORA-06512: at "SYS.DBMS_AQADM_SYS", line 4770ORA-06512: at "SYS.DBMS_AQADM", line 548ORA-06512: at line 1 Other potential errors that may be written to the alert log can be found in the following notes:Document 827184.1 AQ Propagation with CLOB data types Fails with ORA-22990 (11.1)Document 846297.1 AQ Propagation Fails : ORA-00600[kope2upic2954] or Ora-00600[Kghsstream_copyn] (10.2, 11.1)Document 731292.1 ORA-25215 Reported on Local Propagation When Using Transformation with ANYDATA queue tables (10.2, 11.1, 11.2)Document 365093.1 ORA-07445 [kwqppay2aqe()+7360] Reported on Propagation of a Transformed Message (10.1, 10.2)Document 219416.1 Advanced Queuing Propagation Fails with ORA-22922 (9.0)Document 1203544.1 AQ Propagation Aborted with ORA-600 [ociksin: invalid status] on SYS.DBMS_AQADM_SYS.AQ$_PROPAGATION_PROCEDURE After Upgrade (11.1, 11.2)Document 1087324.1 ORA-01405 ORA-01422 reported by Advanced Queuing Propagation schedules after RAC reconfiguration (10.2)Document 1079577.1 Advanced Queuing Propagation Fails With "ORA-22370 incorrect usage of method" (9.2, 10.2, 11.1, 11.2)Document 332792.1 ORA-04061 error relating to SYS.DBMS_PRVTAQIP reported when setting up Statspack (8.1, 9.0, 9.2, 10.1)Document 353325.1 ORA-24056: Internal inconsistency for QUEUE <queue_name> and destination <dblink> (8.1, 9.0, 9.2, 10.1, 10.2, 11.1, 11.2)Document 787367.1 ORA-22275 reported on Propagating Messages with LOB component when propagating between 10.1 and 10.2 (10.1, 10.2)Document 566622.1 ORA-22275 when propagating >4K AQ$_JMS_TEXT_MESSAGEs from 9.2.0.8 to 10.2.0.1 (9.2, 10.1)Document 731539.1 ORA-29268: HTTP client error 401 Unauthorized Error when the AQ Servlet attempts to Propagate a message via HTTP (9.0, 9.2, 10.1, 10.2, 11.1)Document 253131.1 Concurrent Writes May Corrupt LOB Segment When Using Auto Segment Space Management (ORA-1555) (9.2)Document 118884.1 How to unschedule a propagation schedule stuck in pending stateDocument 222992.1 DBMS_AQADM.DISABLE_PROPAGATION_SCHEDULE Returns ORA-24082Document 282987.1 Propagated Messages marked UNDELIVERABLE after Drop and Recreate Of Remote QueueDocument 1204080.1 AQ Propagation Failing With ORA-25329 After Upgraded From 8i or 9i to 10g or 11g.Document 1233675.1 AQ Propagation stops after upgrade to 11.2.0.1 ORA-30757 4.3.1. Errors Related to Incorrect Network Configuration The most common propagation errors result from an incorrect network configuration. The list below contains common errors caused by tnsnames.ora file or database links being configured incorrectly: - ORA-12154: TNS:could not resolve service name- ORA-12505: TNS:listener does not currently know of SID given in connect descriptor- ORA-12514: TNS:listener could not resolve SERVICE_NAME - ORA-12541: TNS-12541 TNS:no listener 4.4. Check the Database Links Exist and are Functioning Correctly For schedules to remote databases confirm the database link exists via. SQL> col DBLINK for a45SQL> select QNAME, NVL(REGEXP_SUBSTR(DESTINATION, '[^@]+', 1, 2), DESTINATION) dblink2 from DBA_QUEUE_SCHEDULES3 where MESSAGE_DELIVERY_MODE = 'PERSISTENT';QNAME DBLINK------------------------------ ---------------------------------------------MY_QUEUE ORCL102B.WORLD Connect as the owner of the link and select across it to verify it works and connects to the database we expect. i.e. select * from ALL_QUEUES@ ORCL102B.WORLD; You need to ensure that the userid that scheduled the propagation (using DBMS_AQADM.SCHEDULE_PROPAGATION or DBMS_PROPAGATION_ADM.CREATE_PROPAGATION if using Streams) has access to the database link for the destination. 4.5. Has Propagation Been Correctly Scheduled? Check that the propagation schedule has been created and that a job queue process has been assigned. Look for the entry in DBA_QUEUE_SCHEDULES and SYS.AQ$_SCHEDULES for your schedule. For 10g and below, check that it has a JOBNO entry in SYS.AQ$_SCHEDULES, and that there is an entry in DBA_JOBS with that JOBNO. For 11g and above, check that the schedule has a JOB_NAME entry in SYS.AQ$_SCHEDULES, and that there is an entry in DBA_SCHEDULER_JOBS with that JOB_NAME. Check the destination is as intended and spelled correctly. SQL> select SCHEMA, QNAME, DESTINATION, SCHEDULE_DISABLED, PROCESS_NAME from DBA_QUEUE_SCHEDULES;SCHEMA QNAME DESTINATION S PROCESS------- ---------- ------------------ - -----------AQADM MULTIPLEQ AQ$_LOCAL N J000 AQ$_LOCAL in the destination column shows that the queue to which we are propagating to is in the same database as the source queue. If the propagation was to a remote (different) database, a database link will be in the DESTINATION column. The entry in the SCHEDULE_DISABLED column, N, means that the schedule is NOT disabled. If Y (yes) appears in this column, propagation is disabled and the schedule will not be executed. If not using Oracle Streams, propagation should resume once you have enabled the schedule by invoking DBMS_AQADM.ENABLE_PROPAGATION_SCHEDULE (for 10.2 Oracle Streams and above, the DBMS_PROPAGATION_ADM.START_PROPAGATION procedure should be used). The PROCESS_NAME is the name of the job queue process currently allocated to execute the schedule. This process is allocated dynamically at execution time. If the PROCESS_NAME column is null (empty) the schedule is not currently executing. You may need to execute this statement a number of times to verify if a process is being allocated. If a process is at some time allocated to the schedule, it is attempting to execute. SQL> select SCHEMA, QNAME, LAST_RUN_DATE, NEXT_RUN_DATE from DBA_QUEUE_SCHEDULES;SCHEMA QNAME LAST_RUN_DATE NEXT_RUN_DATE------ ----- ----------------------- ----------------------- AQADM MULTIPLEQ 13-FEB-2002 13:18:57 13-FEB-2002 13:20:30 In 11g, these dates are expressed in TIMESTAMP WITH TIME ZONE datatypes. If the NEXT_RUN_DATE and NEXT_RUN_TIME columns are null when this statement is executed, the scheduled propagation is currently in progress. If they never change it would suggest that the schedule itself is never executing. If the next scheduled execution is too far away, change the NEXT_TIME parameter of the schedule so that schedules are executed more frequently (assuming that the window is not set to be infinite). Parameters of a schedule can be changed using the DBMS_AQADM.ALTER_PROPAGATION_SCHEDULE call. In 10g and below, scheduling propagation posts a job in the DBA_JOBS view. The columns are more or less the same as DBA_QUEUE_SCHEDULES so you just need to recognize the job and verify that it exists. SQL> select JOB, WHAT from DBA_JOBS where WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%';JOB WHAT---- ----------------- 720 next_date := sys.dbms_aqadm.aq$_propaq(job); For 11g, scheduling propagation posts a job in DBA_SCHEDULER_JOBS instead: SQL> select JOB_NAME from DBA_SCHEDULER_JOBS where JOB_NAME like 'AQ_JOB$_%';JOB_NAME------------------------------AQ_JOB$_41 If no job exists, check DBA_QUEUE_SCHEDULES to make sure that the schedule has not been disabled. For 10g and below, the job number is dynamic for AQ propagation schedules. The procedure that is executed to expedite a propagation schedule runs, removes itself from DBA_JOBS, and then reposts a new job for the next scheduled propagation. The job number should therefore always increment unless the schedule has been set up to run indefinitely. 4.6. Is the Schedule Executing but Failing to Complete? Run the following query: SQL> select FAILURES, LAST_ERROR_MSG from DBA_QUEUE_SCHEDULES;FAILURES LAST_ERROR_MSG------------ -----------------------1 ORA-25207: enqueue failed, queue AQADM.INQ is disabled from enqueueingORA-02063: preceding line from SHANE816 The failures column shows how many times we have attempted to execute the schedule and failed. Oracle will attempt to execute the schedule 16 times after which it will be removed from the DBA_JOBS or DBA_SCHEDULER_JOBS view and the schedule will become disabled. The column DBA_QUEUE_SCHEDULES.SCHEDULE_DISABLED will show 'Y'. For 11g and above, the DBA_SCHEDULER_JOBS.STATE column will show 'BROKEN' for the job corresponding to DBA_QUEUE_SCHEDULES.JOB_NAME. Prior to 10g the back off algorithm for failures was exponential, whereas from 10g onwards it is linear. The propagation will become disabled on the 17th attempt. Only the last execution failure will be reflected in the LAST_ERROR_MSG column. That is, if the schedule fails 5 times for 5 different reasons, only the last set of errors will be recorded in DBA_QUEUE_SCHEDULES. Any errors need to be resolved to allow propagation to continue. If propagation has also become disabled due to 17 failures, first resolve the reason for the error and then re-enable the schedule using the DBMS_AQADM.ENABLE_PROPAGATION_SCHEDULE procedure, or DBMS_PROPAGATION_ADM.START_PROPAGATION if using 10.2 or above Oracle Streams. As soon as the schedule executes successfully the error message entries will be deleted. Oracle does not keep a history of past failures. However, when using Oracle Streams, the errors will be retained in the DBA_PROPAGATION view even after the schedule resumes successfully. See the following note for instructions on how to clear out the errors from the DBA_PROPAGATION view:Document 808136.1 How to clear the old errors from DBA_PROPAGATION view?If a schedule is active and no errors are being reported then the source queue may not have any messages to be propagated. 4.7. Do the Propagation Notification Queue Table and Queue Exist? Check to see that the propagation notification queue table and queue exist and are enabled for enqueue and dequeue. Propagation makes use of the propagation notification queue for handling propagation run-time events, and the messages in this queue are stored in a SYS-owned queue table. This queue should never be stopped or dropped and the corresponding queue table never be dropped. 10g and belowThe propagation notification queue table is of the format SYS.AQ$_PROP_TABLE_n, where 'n' is the RAC instance number, i.e. '1' for a non-RAC environment. This queue and queue table are created implicitly when propagation is first scheduled. If propagation has been scheduled and these objects do not exist, try unscheduling and rescheduling propagation. If they still do not exist contact Oracle Support. SQL> select QUEUE_TABLE from DBA_QUEUE_TABLES2 where QUEUE_TABLE like '%PROP_TABLE%' and OWNER = 'SYS';QUEUE_TABLE------------------------------AQ$_PROP_TABLE_1SQL> select NAME, ENQUEUE_ENABLED, DEQUEUE_ENABLED2 from DBA_QUEUES where owner='SYS'3 and QUEUE_TABLE like '%PROP_TABLE%';NAME ENQUEUE DEQUEUE------------------------------ ------- -------AQ$_PROP_NOTIFY_1 YES YESAQ$_AQ$_PROP_TABLE_1_E NO NO If the AQ$_PROP_NOTIFY_1 queue is not enabled for enqueue or dequeue, it should be so enabled using DBMS_AQADM.START_QUEUE. However, the exception queue AQ$_AQ$_PROP_TABLE_1_E should not be enabled for enqueue or dequeue.11g and aboveThe propagation notification queue table is of the format SYS.AQ_PROP_TABLE, and is created when the database is created. If they do not exist, contact Oracle Support. SQL> select QUEUE_TABLE from DBA_QUEUE_TABLES2 where QUEUE_TABLE like '%PROP_TABLE%' and OWNER = 'SYS';QUEUE_TABLE------------------------------AQ_PROP_TABLESQL> select NAME, ENQUEUE_ENABLED, DEQUEUE_ENABLED2 from DBA_QUEUES where owner='SYS'3 and QUEUE_TABLE like '%PROP_TABLE%';NAME ENQUEUE DEQUEUE------------------------------ ------- -------AQ_PROP_NOTIFY YES YESAQ$_AQ_PROP_TABLE_E NO NO If the AQ_PROP_NOTIFY queue is not enabled for enqueue or dequeue, it should be so enabled using DBMS_AQADM.START_QUEUE. However, the exception queue AQ$_AQ$_PROP_TABLE_E should not be enabled for enqueue or dequeue. 4.8. Does the Remote Queue Exist and is it Enabled for Enqueueing? Check that the remote queue the propagation is transferring messages to exists and is enabled for enqueue: SQL> select DESTINATION from USER_QUEUE_SCHEDULES where QNAME = 'OUTQ';DESTINATION-----------------------------------------------------------------------------"AQADM"."INQ"@M2V102.ESSQL> select OWNER, NAME, ENQUEUE_ENABLED, DEQUEUE_ENABLED from [email protected];OWNER NAME ENQUEUE DEQUEUE-------- ------ ----------- -----------AQADM INQ YES YES 4.9. Do the Target and Source Database Charactersets Differ? If a message fails to propagate, check the database charactersets of the source and target databases. Investigate whether the same message can propagate between the databases with the same characterset or it is only a particular combination of charactersets which causes a problem. 4.10. Check the Queue Table Type Agreement Propagation is not possible between queue tables which have types that differ in some respect. One way to determine if this is the case is to run the DBMS_AQADM.VERIFY_QUEUE_TYPES procedure for the two queues that the propagation operates on. If the types do not agree, DBMS_AQADM.VERIFY_QUEUE_TYPES will return '0'.For AQ propagation between databases which have different NLS_LENGTH_SEMANTICS settings, propagation will not work, unless the queues are Oracle Streams ANYDATA queues.See the following notes for issues caused by lack of type agreement:Document 1079577.1 Advanced Queuing Propagation Fails With "ORA-22370: incorrect usage of method"Document 282987.1 Propagated Messages marked UNDELIVERABLE after Drop and Recreate Of Remote QueueDocument 353754.1 Streams Messaging Propagation Fails between Single and Multi-byte Charactersets when using Chararacter Length Semantics in the ADT 4.11. Enable Propagation Tracing 4.11.1. System Level This is set it in the init.ora/spfile as follows: event="24040 trace name context forever, level 10" and restart the instanceThis event cannot be set dynamically with an alter system command until version 10.2: SQL> alter system set events '24040 trace name context forever, level 10'; To unset the event: SQL> alter system set events '24040 trace name context off'; Debugging information will be logged to job queue trace file(s) (jnnn) as propagation takes place. You can check the trace file for errors, and for statements indicating that messages have been sent. For the most part the trace information is understandable. This trace should also be uploaded to Oracle Support if a service request is created. 4.11.2. Attaching to a Specific Process We can also attach to an existing job queue processes that is running a propagation schedule and trace it individually using the oradebug utility, as follows:10.2 and below connect / as sysdbaselect p.SPID, p.PROGRAM from v$PROCESS p, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j where s.SID=jr.SID and s.PADDR=p.ADDR and jr.JOB=j.JOB and j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%';-- For the process id (SPID) attach to it via oradebug and generate the following traceoradebug setospid <SPID>oradebug unlimitoradebug Event 10046 trace name context forever, level 12oradebug Event 24040 trace name context forever, level 10-- Trace the process for 5 minutesoradebug Event 10046 trace name context offoradebug Event 24040 trace name context off-- The following command returns the pathname/filename to the file being written tooradebug tracefile_name 11g connect / as sysdbacol PROGRAM for a30select p.SPID, p.PROGRAM, j.JOB_NAMEfrom v$PROCESS p, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j where s.SID=jr.SESSION_ID and s.PADDR=p.ADDR and jr.JOB_NAME=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%';-- For the process id (SPID) attach to it via oradebug and generate the following traceoradebug setospid <SPID>oradebug unlimitoradebug Event 10046 trace name context forever, level 12oradebug Event 24040 trace name context forever, level 10-- Trace the process for 5 minutesoradebug Event 10046 trace name context offoradebug Event 24040 trace name context off-- The following command returns the pathname/filename to the file being written tooradebug tracefile_name 4.11.3. Further Tracing The previous tracing steps only trace the job queue process executing the propagation on the source. At times it is useful to trace the propagation receiver process (the session which is enqueueing the messages into the target queue) on the target database which is associated with the job queue process on the source database.These following queries provide ways of identifying the processes involved in propagation so that you can attach to them via oradebug to generate trace information.In order to identify the propagation receiver process you need to execute the query as a user with privileges to access the v$ views in both the local and remote databases so the database link must connect as a user with those privileges in the remote database. The <DBLINK> in the queries should be replaced by the appropriate database link.The queries have two forms due to the differences between operating systems. The value returned by 'Rem Process' is the operating system identifier of the propagation receiver on the remote database. Once identified, this process can be attached to and traced on the remote database using the commands given in Section 4.11.2.10.2 and below - Windows select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from v$PROCESS pl, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SID and s.PADDR=pl.ADDR and jr.JOB=j.JOB and j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%' and pl.SPID=substr(sr.PROCESS, instr(sr.PROCESS,':')+1); 10.2 and below - Unix select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from V$PROCESS pl, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SID and s.PADDR=pl.ADDR and jr.JOB=j.JOB and j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%' and pl.SPID=sr.PROCESS; 11g - Windows select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from V$PROCESS pl, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SESSION_ID and s.PADDR=pl.ADDR and jr.JOB_NAME=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%%' and pl.SPID=substr(sr.PROCESS, instr(sr.PROCESS,':')+1); 11g - Unix select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from V$PROCESS pl, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SESSION_ID and s.PADDR=pl.ADDR and jr.JOB_NAME=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%%' and pl.SPID=sr.PROCESS;   5. Additional Troubleshooting Steps for AQ Propagation of User-Enqueued and Dequeued Messages 5.1. Check the Privileges of All Users Involved Ensure that the owner of the database link has the necessary privileges on the aq packages. SQL> select TABLE_NAME, PRIVILEGE from USER_TAB_PRIVS;TABLE_NAME PRIVILEGE------------------------------ ----------------------------------------DBMS_LOCK EXECUTEDBMS_AQ EXECUTEDBMS_AQADM EXECUTEDBMS_AQ_BQVIEW EXECUTEQT52814_BUFFER SELECT Note that when queue table is created, a view called QT<nnn>_BUFFER is created in the SYS schema, and the queue table owner is given SELECT privileges on it. The <nnn> corresponds to the object_id of the associated queue table. SQL> select * from USER_ROLE_PRIVS;USERNAME GRANTED_ROLE ADM DEF OS_------------------------------ ------------------------------ ---- ---- ---AQ_USER1 AQ_ADMINISTRATOR_ROLE NO YES NOAQ_USER1 CONNECT NO YES NOAQ_USER1 RESOURCE NO YES NO It is good practice to configure central AQ administrative user. All admin and processing jobs are created, executed and administered as this user. This configuration is not mandatory however, and the database link can be owned by any existing queue user. If this latter configuration is used, ensure that the connecting user has the necessary privileges on the AQ packages and objects involved. Privileges for an AQ Administrative user Execute on DBMS_AQADM Execute on DBMS_AQ Granted the AQ_ADMINISTRATOR_ROLE Privileges for an AQ user Execute on DBMS_AQ Execute on the message payload Enqueue privileges on the remote queue Dequeue privileges on the originating queue Privileges need to be confirmed on both sites when propagation is scheduled to remote destinations. Verify that the user ID used to login to the destination through the database link has been granted privileges to use AQ. 5.2. Verify Queue Payload Types AQ will not propagate messages from one queue to another if the payload types of the two queues are not verified to be equivalent. An AQ administrator can verify if the source and destination's payload types match by executing the DBMS_AQADM.VERIFY_QUEUE_TYPES procedure. The results of the type checking will be stored in the SYS.AQ$_MESSAGE_TYPES table. This table can be accessed using the object identifier OID of the source queue and the address database link of the destination queue, i.e. [schema.]queue_name[@destination]. Prior to Oracle 9i the payload (message type) had to be the same for all the queue tables involved in propagation. From Oracle9i onwards a transformation can be used so that payloads can be converted from one type to another. The following procedural call made on the source database can verify whether we can propagate between the source and the destination queue tables. connect aq_user1/[email protected] serverout onDECLARErc_value number;BEGINDBMS_AQADM.VERIFY_QUEUE_TYPES(src_queue_name => 'AQ_USER1.Q_1', dest_queue_name => 'AQ_USER2.Q_2',destination => 'dbl_aq_user2.es',rc => rc_value);dbms_output.put_line('rc_value code is '||rc_value);END;/ If propagation is possible then the return code value will be 1. If it is 0 then propagation is not possible and further investigation of the types and transformations used by and in conjunction with the queue tables is required. With regard to comparison of the types the following sql can be used to extract the DDL for a specific type with' %' changed appropriately on the source and target. This can then be compared for the source and target. SET LONG 20000 set pagesize 50 EXECUTE DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM, 'STORAGE',false); SELECT DBMS_METADATA.GET_DDL('TYPE',t.type_name) from user_types t WHERE t.type_name like '%'; EXECUTE DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM, 'DEFAULT'); 5.3. Check Message State and Destination The first step in this process is to identify the queue table associated with the problem source queue. Although you schedule propagation for a specific queue, most of the meta-data associated with that queue is stored in the underlying queue table. The following statement finds the queue table for a given queue (note that this is a multiple-consumer queue table). SQL> select QUEUE_TABLE from DBA_QUEUES where NAME = 'MULTIPLEQ';QUEUE_TABLE --------------------MULTIPLEQTABLE For a small amount of messages in a multiple-consumer queue table, the following query can be run: SQL> select MSG_STATE, CONSUMER_NAME, ADDRESS from AQ$MULTIPLEQTABLE where QUEUE = 'MULTIPLEQ';MSG_STATE CONSUMER_NAME ADDRESS-------------- ----------------------- -------------READY AQUSER2 [email protected] AQUSER1READY AQUSER3 AQADM.INQ In this example we see 2 messages ready to be propagated to remote queues and 1 that is not. If the address column is blank, the message is not scheduled for propagation and can only be dequeued from the queue upon which it was enqueued. The MSG_STATE column values are discussed in Document 102330.1 Advanced Queueing MSG_STATE Values and their Interpretation. If the address column has a value, the message has been enqueued for propagation to another queue. The first row in the example includes a database link (@M2V102.ES). This demonstrates that the message should be propagated to a queue at a remote database. The third row does not include a database link so will be propagated to a queue that resides on the same database as the source queue. The consumer name is the intended recipient at the target queue. Note that we are not querying the base queue table directly; rather, we are querying a view that is available on top of every queue table, AQ$<queue_table_name>.A more realistic query in an environment where the queue table contains thousands of messages is8.0.3-compatible multiple-consumer queue table and all compatibility single-consumer queue tables select count(*), MSG_STATE, QUEUE from AQ$<queue_table_name>  group by MSG_STATE, QUEUE; 8.1.3 and 10.0-compatible queue tables select count(*), MSG_STATE, QUEUE, CONSUMER_NAME from AQ$<queue_table_name>group by MSG_STATE, QUEUE, CONSUMER_NAME; For multiple-consumer queue tables, if you did not see the expected CONSUMER_NAME , check the syntax of the enqueue code and verify the recipients are declared correctly. If a recipients list is not used on enqueue, check the subscriber list in the AQ$_<queue_table_name>_S view (note that a single-consumer queue table does not have a subscriber view. This view records all members of the default subscription list which were added using the DBMS_AQADM.ADD_SUBSCRIBER procedure and also those enqueued using a recipient list. SQL> select QUEUE, NAME, ADDRESS from AQ$MULTIPLEQTABLE_S;QUEUE NAME ADDRESS---------- ----------- -------------MULTIPLEQ AQUSER2 [email protected] AQUSER1 In this example we have 2 subscribers registered with the queue. We have a local subscriber AQUSER1, and a remote subscriber AQUSER2, on the queue INQ, owned by AQADM, at M2V102.ES. Unless overridden with a recipient list during enqueue every message enqueued to this queue will be propagated to INQ at M2V102.ES.For 8.1 style and above multiple consumer queue tables, you can also check the following information at the target: select CONSUMER_NAME, DEQ_TXN_ID, DEQ_TIME, DEQ_USER_ID, PROPAGATED_MSGID from AQ$<queue_table_name> where QUEUE = '<QUEUE_NAME>'; For 8.0 style queues, if the queue table supports multiple consumers you can obtain the same information from the history column of the queue table: select h.CONSUMER, h.TRANSACTION_ID, h.DEQ_TIME, h.DEQ_USER, h.PROPAGATED_MSGIDfrom AQ$<queue_table_name> t, table(t.history) h where t.Q_NAME = '<QUEUE_NAME>'; A non-NULL TRANSACTION_ID indicates that the message was successfully propagated. Further, the DEQ_TIME indicates the time of propagation, the DEQ_USER indicates the userid used for propagation, and the PROPAGATED_MSGID indicates the message ID of the message that was enqueued at the destination. 6. Additional Troubleshooting Steps for Propagation in an Oracle Streams Environment 6.1. Is the Propagation Enabled? For a propagation job to propagate messages, the propagation must be enabled. For Streams, a special view called DBA_PROPAGATION exists to convey information about Streams propagations. If messages are not being propagated by a propagation as expected, then the propagation might not be enabled. To query for this: SELECT p.PROPAGATION_NAME, DECODE(s.SCHEDULE_DISABLED, 'Y', 'Disabled','N', 'Enabled') SCHEDULE_DISABLED, s.PROCESS_NAME, s.FAILURES, s.LAST_ERROR_MSGFROM DBA_QUEUE_SCHEDULES s, DBA_PROPAGATION pWHERE p.DESTINATION_DBLINK = NVL(REGEXP_SUBSTR(s.DESTINATION, '[^@]+', 1, 2), s.DESTINATION) AND s.SCHEMA = p.SOURCE_QUEUE_OWNER AND s.QNAME = p.SOURCE_QUEUE_NAME AND MESSAGE_DELIVERY_MODE = 'PERSISTENT' order by PROPAGATION_NAME; At times, the propagation job may become "broken" or fail to start after an error has been encountered or after a database restart. If an error is indicated by the above query, an attempt to disable the propagation and then re-enable it can be made. In the examples below, for the propagation named STRMADMIN_PROPAGATE where the queue name is STREAMS_QUEUE owned by STRMADMIN and the destination database link is ORCL2.WORLD, the commands would be:10.2 and above exec dbms_propagation_adm.stop_propagation('STRMADMIN_PROPAGATE'); exec dbms_propagation_adm.start_propagation('STRMADMIN_PROPAGATE'); If the above does not fix the problem, stop the propagation specifying the force parameter (2nd parameter on stop_propagation) as TRUE: exec dbms_propagation_adm.stop_propagation('STRMADMIN_PROPAGATE',true); exec dbms_propagation_adm.start_propagation('STRMADMIN_PROPAGATE'); The statistics for the propagation as well as any old error messages are cleared when the force parameter is set to TRUE. Therefore if the propagation schedule is stopped with FORCE set to TRUE, and upon restart there is still an error message in DBA_PROPAGATION, then the error message is current.9.2 or 10.1 exec dbms_aqadm.disable_propagation_schedule('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); exec dbms.aqadm.enable_propagation_schedule('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); If the above does not fix the problem, perform an unschedule of propagation and then schedule_propagation: exec dbms_aqadm.unschedule_propagation('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); exec dbms_aqadm.schedule_propagation('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); Typically if the error from the first query in Section 6.1 recurs after restarting the propagation as shown above, further troubleshooting of the error is needed. 6.2. Check Propagation Rule Sets and Transformations Inspect the configuration of the rules in the rule set that is associated with the propagation process to make sure that they evaluate to TRUE as expected. If not, then the object or schema will not be propagated. Remember that when a negative rule evaluates to TRUE, the specified object or schema will not be propagated. Finally inspect any rule-based transformations that are implemented with propagation to make sure they are changing the data in the intended way.The following query shows what rule sets are assigned to a propagation: select PROPAGATION_NAME, RULE_SET_OWNER||'.'||RULE_SET_NAME "Positive Rule Set",NEGATIVE_RULE_SET_OWNER||'.'||NEGATIVE_RULE_SET_NAME "Negative Rule Set"from DBA_PROPAGATION; The next two queries list the propagation rules and their conditions. The first is for the positive rule set, the second is for the negative rule set: set long 4000select rsr.RULE_SET_OWNER||'.'||rsr.RULE_SET_NAME RULE_SET ,rsr.RULE_OWNER||'.'||rsr.RULE_NAME RULE_NAME,r.RULE_CONDITION CONDITION fromDBA_RULE_SET_RULES rsr, DBA_RULES rwhere rsr.RULE_NAME = r.RULE_NAME and rsr.RULE_OWNER = r.RULE_OWNER and RULE_SET_NAME in(select RULE_SET_NAME from DBA_PROPAGATION) order by rsr.RULE_SET_OWNER, rsr.RULE_SET_NAME;   set long 4000select c.PROPAGATION_NAME, rsr.RULE_SET_OWNER||'.'||rsr.RULE_SET_NAME RULE_SET ,rsr.RULE_OWNER||'.'||rsr.RULE_NAME RULE_NAME,r.RULE_CONDITION CONDITION fromDBA_RULE_SET_RULES rsr, DBA_RULES r ,DBA_PROPAGATION cwhere rsr.RULE_NAME = r.RULE_NAME and rsr.RULE_OWNER = r.RULE_OWNER andrsr.RULE_SET_OWNER=c.NEGATIVE_RULE_SET_OWNER and rsr.RULE_SET_NAME=c.NEGATIVE_RULE_SET_NAMEand rsr.RULE_SET_NAME in(select NEGATIVE_RULE_SET_NAME from DBA_PROPAGATION) order by rsr.RULE_SET_OWNER, rsr.RULE_SET_NAME; 6.3. Determining the Total Number of Messages and Bytes Propagated As in Section 3.1, determining if messages are flowing can be instructive to see whether the propagation is entirely hung or just slow. If the propagation is not in flow control (see Section 6.5.2), but the statistics are incrementing slowly, there may be a performance issue. For Streams implementations two views are available that can assist with this that can show the number of messages sent by a propagation, as well as the number of acknowledgements being returned from the target site: the V$PROPAGATION_SENDER view at the Source site and the V$PROPAGATION_RECEIVER view at the destination site. It is helpful to query both to determine if messages are being delivered to the target. Look for the statistics to increase.Source: select QUEUE_SCHEMA, QUEUE_NAME, DBLINK,HIGH_WATER_MARK, ACKNOWLEDGEMENT, TOTAL_MSGS, TOTAL_BYTESfrom V$PROPAGATION_SENDER; Target: select SRC_QUEUE_SCHEMA, SRC_QUEUE_NAME, SRC_DBNAME, DST_QUEUE_SCHEMA, DST_QUEUE_NAME, HIGH_WATER_MARK, ACKNOWLEDGEMENT, TOTAL_MSGS from V$PROPAGATION_RECEIVER; 6.4. Check Buffered Subscribers The V$BUFFERED_SUBSCRIBERS view displays information about subscribers for all buffered queues in the instance. This view can be queried to make sure that the site that the propagation is propagating to is listed as a subscriber address for the site being propagated from: select QUEUE_SCHEMA, QUEUE_NAME, SUBSCRIBER_ADDRESS from V$BUFFERED_SUBSCRIBERS; The SUBSCRIBER_ADDRESS column will not be populated when the propagation is local (between queues on the same database). 6.5. Common Streams Propagation Errors 6.5.1. ORA-02082: A loopback database link must have a connection qualifier. This error can occur if you use the Streams Setup Wizard in Oracle Enterprise Manager without first configuring the GLOBAL_NAME for your database. 6.5.2. ORA-25307: Enqueue rate too high. Enable flow control DBA_QUEUE_SCHEDULES will display this informational message for propagation when the automatic flow control (10g feature of Streams) has been invoked.Similar to Streams capture processes, a Streams propagation process can also go into a state of 'flow control. This is an informative message that indicates flow control has been automatically enabled to reduce the rate at which messages are being enqueued into at target queue.This typically occurs when the target site is unable to keep up with the rate of messages flowing from the source site. Other than checking that the apply process is running normally on the target site, usually no action is required by the DBA. Propagation and the capture process will be resumed automatically when the target site is able to accept more messages.The following document contains more information:Document 302109.1 Streams Propagation Error: ORA-25307 Enqueue rate too high. Enable flow controlSee the following document for one potential cause of this situation:Document 1097115.1 Oracle Streams Apply Reader is in 'Paused' State 6.5.3. ORA-25315 unsupported configuration for propagation of buffered messages This error typically occurs when the target database is RAC and usually indicates that an attempt was made to propagate buffered messages with the database link pointing to an instance in the destination database which is not the owner instance of the destination queue. To resolve the problem, use queue-to-queue propagation for buffered messages. 6.5.4. ORA-600 [KWQBMCRCPTS101] after dropping / recreating propagation For cause/fixes refer to:Document 421237.1 ORA-600 [KWQBMCRCPTS101] reported by a Qmon slave process after dropping a Streams Propagation 6.5.5. Stopping or Dropping a Streams Propagation Hangs See the following note:Document 1159787.1 Troubleshooting Streams Propagation When It is Not Functioning and Attempts to Stop It Hang 6.6. Streams Propagation-Related Notes for Common Issues Document 437838.1 Streams Specific PatchesDocument 749181.1 How to Recover Streams After Dropping PropagationDocument 368912.1 Queue to Queue Propagation Schedule encountered ORA-12514 in a RAC environmentDocument 564649.1 ORA-02068/ORA-03114/ORA-03113 Errors From Streams Propagation Process - Remote Database is Available and Unschedule/Reschedule Does Not ResolveDocument 553017.1 Stream Propagation Process Errors Ora-4052 Ora-6554 From 11g To 10201Document 944846.1 Streams Propagation Fails Ora-7445 [kohrsmc]Document 745601.1 ORA-23603 'STREAMS enqueue aborted due to low SGA' Error from Streams Propagation, and V$STREAMS_CAPTURE.STATE Hanging on 'Enqueuing Message'Document 333068.1 ORA-23603: Streams Enqueue Aborted Eue To Low SGADocument 363496.1 Ora-25315 Propagating on RAC StreamsDocument 368237.1 Unable to Unschedule Propagation. Streams Queue is InvalidDocument 436332.1 dbms_propagation_adm.stop_propagation hangsDocument 727389.1 Propagation Fails With ORA-12528Document 730911.1 ORA-4063 Is Reported After Dropping Negative Prop.RulesetDocument 460471.1 Propagation Blocked by Qmon Process - Streams_queue_table / 'library cache lock' waitsDocument 1165583.1 ORA-600 [kwqpuspse0-ack] In Streams EnvironmentDocument 1059029.1 Combined Capture and Apply (CCA) : Capture aborts : ORA-1422 after schedule_propagationDocument 556309.1 Changing Propagation/ queue_to_queue : false -> true does does not work; no LCRs propagatedDocument 839568.1 Propagation failing with error: ORA-01536: space quota exceeded for tablespace ''Document 311021.1 Streams Propagation Process : Ora 12154 After Reboot with Transparent Application Failover TAF configuredDocument 359971.1 STREAMS propagation to Primary of physical Standby configuation errors with Ora-01033, Ora-02068Document 1101616.1 DBMS_PROPAGATION_ADM.DROP_PROPAGATION FAILS WITH ORA-1747 7. Performance Issues A propagation may seem to be slow if the queries from Sections 3.1 and 6.3 show that the message statistics are not changing quickly. In Oracle Streams, this more usually is due to a slow apply process at the target rather than a slow propagation. Propagation could be inferred to be slow if the message statistics are changing, and the state of a capture process according to V$STREAMS_CAPTURE.STATE is PAUSED FOR FLOW CONTROL, but an ORA-25307 'Enqueue rate too high. Enable flow control' warning is NOT observed in DBA_QUEUE_SCHEDULES per Section 6.5.2. If this is the case, see the following notes / white papers for suggestions to increase performance:Document 335516.1 Master Note for Streams Performance RecommendationsDocument 730036.1 Overview for Troubleshooting Streams Performance IssuesDocument 780733.1 Streams Propagation Tuning with Network ParametersWhite Paper: http://www.oracle.com/technetwork/database/features/availability/maa-wp-10gr2-streams-performance-130059.pdfWhite Paper: Oracle Streams Configuration Best Practices: Oracle Database 10g Release 10.2, http://www.oracle.com/technetwork/database/features/availability/maa-10gr2-streams-configuration-132039.pdf, See APPENDIX A: USING STREAMS CONFIGURATIONS OVER A NETWORKFor basic AQ propagation, the network tuning in the aforementioned Appendix A of the white paper 'Oracle Streams Configuration Best Practices: Oracle Database 10g Release 10.2' is applicable. References NOTE:102330.1 - Advanced Queueing MSG_STATE Values and their InterpretationNOTE:102771.1 - Advanced Queueing Propagation using PL/SQLNOTE:1059029.1 - Combined Capture and Apply (CCA) : Capture aborts : ORA-1422 after schedule_propagationNOTE:1079577.1 - Advanced Queuing Propagation Fails With "ORA-22370: incorrect usage of method"NOTE:1083608.1 - 11g Streams and Oracle SchedulerNOTE:1087324.1 - ORA-01405 ORA-01422 reported by Adavanced Queueing Propagation schedules after RAC reconfigurationNOTE:1097115.1 - Oracle Streams Apply Reader is in 'Paused' StateNOTE:1101616.1 - DBMS_PROPAGATION_ADM.DROP_PROPAGATION FAILS WITH ORA-1747NOTE:1159787.1 - Troubleshooting Streams Propagation When It is Not Functioning and Attempts to Stop It HangNOTE:1165583.1 - ORA-600 [kwqpuspse0-ack] In Streams EnvironmentNOTE:118884.1 - How to unschedule a propagation schedule stuck in pending stateNOTE:1203544.1 - AQ PROPAGATION ABORTED WITH ORA-600[OCIKSIN: INVALID STATUS] ON SYS.DBMS_AQADM_SYS.AQ$_PROPAGATION_PROCEDURE AFTER UPGRADENOTE:1204080.1 - AQ Propagation Failing With ORA-25329 After Upgraded From 8i or 9i to 10g or 11g.NOTE:219416.1 - Advanced Queuing Propagation fails with ORA-22922NOTE:222992.1 - DBMS_AQADM.DISABLE_PROPAGATION_SCHEDULE Returns ORA-24082NOTE:253131.1 - Concurrent Writes May Corrupt LOB Segment When Using Auto Segment Space Management (ORA-1555)NOTE:282987.1 - Propagated Messages marked UNDELIVERABLE after Drop and Recreate Of Remote QueueNOTE:298015.1 - Kwqjswproc:Excep After Loop: Assigning To SelfNOTE:302109.1 - Streams Propagation Error: ORA-25307 Enqueue rate too high. Enable flow controlNOTE:311021.1 - Streams Propagation Process : Ora 12154 After Reboot with Transparent Application Failover TAF configuredNOTE:332792.1 - ORA-04061 error relating to SYS.DBMS_PRVTAQIP reported when setting up StatspackNOTE:333068.1 - ORA-23603: Streams Enqueue Aborted Eue To Low SGANOTE:335516.1 - Master Note for Streams Performance RecommendationsNOTE:353325.1 - ORA-24056: Internal inconsistency for QUEUE and destination NOTE:353754.1 - Streams Messaging Propagation Fails between Single and Multi-byte Charactersets when using Chararacter Length Semantics in the ADT.NOTE:359971.1 - STREAMS propagation to Primary of physical Standby configuation errors with Ora-01033, Ora-02068NOTE:363496.1 - Ora-25315 Propagating on RAC StreamsNOTE:365093.1 - ORA-07445 [kwqppay2aqe()+7360] reported on Propagation of a Transformed MessageNOTE:368237.1 - Unable to Unschedule Propagation. Streams Queue is InvalidNOTE:368912.1 - Queue to Queue Propagation Schedule encountered ORA-12514 in a RAC environmentNOTE:421237.1 - ORA-600 [KWQBMCRCPTS101] reported by a Qmon slave process after dropping a Streams PropagationNOTE:436332.1 - dbms_propagation_adm.stop_propagation hangsNOTE:437838.1 - Streams Specific PatchesNOTE:460471.1 - Propagation Blocked by Qmon Process - Streams_queue_table / 'library cache lock' waitsNOTE:463820.1 - Streams Combined Capture and Apply in 11gNOTE:553017.1 - Stream Propagation Process Errors Ora-4052 Ora-6554 From 11g To 10201NOTE:556309.1 - Changing Propagation/ queue_to_queue : false -> true does does not work; no LCRs propagatedNOTE:564649.1 - ORA-02068/ORA-03114/ORA-03113 Errors From Streams Propagation Process - Remote Database is Available and Unschedule/Reschedule Does Not ResolveNOTE:566622.1 - ORA-22275 when propagating >4K AQ$_JMS_TEXT_MESSAGEs from 9.2.0.8 to 10.2.0.1NOTE:727389.1 - Propagation Fails With ORA-12528NOTE:730036.1 - Overview for Troubleshooting Streams Performance IssuesNOTE:730911.1 - ORA-4063 Is Reported After Dropping Negative Prop.RulesetNOTE:731292.1 - ORA-25215 Reported On Local Propagation When Using Transformation with ANYDATA queue tablesNOTE:731539.1 - ORA-29268: HTTP client error 401 Unauthorized Error when the AQ Servlet attempts to Propagate a message via HTTPNOTE:745601.1 - ORA-23603 'STREAMS enqueue aborted due to low SGA' Error from Streams Propagation, and V$STREAMS_CAPTURE.STATE Hanging on 'Enqueuing Message'NOTE:749181.1 - How to Recover Streams After Dropping PropagationNOTE:780733.1 - Streams Propagation Tuning with Network ParametersNOTE:787367.1 - ORA-22275 reported on Propagating Messages with LOB component when propagating between 10.1 and 10.2NOTE:808136.1 - How to clear the old errors from DBA_PROPAGATION view ?NOTE:827184.1 - AQ Propagation with CLOB data types Fails with ORA-22990NOTE:827473.1 - How to alter propagation from queue_to_queue to queue_to_dblinkNOTE:839568.1 - Propagation failing with error: ORA-01536: space quota exceeded for tablespace ''NOTE:846297.1 - AQ Propagation Fails : ORA-00600[kope2upic2954] or Ora-00600[Kghsstream_copyn]NOTE:944846.1 - Streams Propagation Fails Ora-7445 [kohrsmc]

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• Exploring packages in code

  In my previous post Searching for tasks with code you can see how to explore the control flow side of packages, drilling down through containers, task, and event handlers, but it didn’t cover the data flow. I recently saw a post on the MSDN forum asking how to edit an existing package programmatically, and the sticking point was how to find the the data flow and the components inside. This post builds on some of the previous code and shows how you can explore all objects inside a package. I took the sample Task Search application I’d written previously, and came up with a totally pointless little console application that just walks through the package and writes out the basic type and name of every object it finds, starting with the package itself e.g. Package – MyPackage . The sample package we used last time showed nested objects as well an event handler; a OnPreExecute event tucked away on the task SQL In FEL. The output of this sample tool would look like this: PackageObjects v1.0.0.0 (1.0.0.26627) Copyright (C) 2009 Konesans Ltd Processing File - Z:\Users\Darren Green\Documents\Visual Studio 2005\Projects\SSISTestProject\EventsAndContainersWithExe cSQLForSearch.dtsx Package - EventsAndContainersWithExecSQLForSearch For Loop - FOR Counter Loop Task - SQL In Counter Loop Sequence Container - SEQ For Each Loop Wrapper For Each Loop - FEL Simple Loop Task - SQL In FEL Task - SQL On Pre Execute for FEL SQL Task Sequence Container - SEQ Top Level Sequence Container - SEQ Nested Lvl 1 Sequence Container - SEQ Nested Lvl 2 Task - SQL In Nested Lvl 2 Task - SQL In Nested Lvl 1 #1 Task - SQL In Nested Lvl 1 #2 Connection Manager – LocalHost The code is very similar to what we had previously, but there are a couple of extra bits to deal with connections and to look more closely at a task and see if it is a Data Flow task. For connections your just examine the package's Connections collection as shown in the abridged snippets below. First you can see the call to the ProcessConnections method, followed by the method itself. // Load the package file Application application = new Application(); using (Package package = application.LoadPackage(filename, null)) { // Write out the package name Console.WriteLine("Package - {0}", package.Name); ... More ... // Look and the connections ProcessConnections(package.Connections); } private static void ProcessConnections(Connections connections) { foreach (ConnectionManager connectionManager in connections) { Console.WriteLine("Connection Manager - {0}", connectionManager.Name); } } What we didn’t see in the sample output above was anything to do with the Data Flow, but rest assured the code now handles it too. The following snippet shows how each task is examined to see if it is a Data Flow task, and if so we can then loop through all of the components inside the data flow. private static void ProcessTaskHost(TaskHost taskHost) { if (taskHost == null) { return; } Console.WriteLine("Task - {0}", taskHost.Name); // Check if the task is a Data Flow task MainPipe pipeline = taskHost.InnerObject as MainPipe; if (pipeline != null) { ProcessPipeline(pipeline); } } private static void ProcessPipeline(MainPipe pipeline) { foreach (IDTSComponentMetaData90 componentMetadata in pipeline.ComponentMetaDataCollection) { Console.WriteLine("Pipeline Component - {0}", componentMetadata.Name); // If you wish to make changes to the component then you should really use the managed wrapper. // CManagedComponentWrapper wrapper = componentMetadata.Instantiate(); // wrapper.SetComponentProperty("PropertyName", "Value"); } } Hopefully you can see how we get a reference to the Data Flow task, and then use the ComponentMetaDataCollection to find out what components we have inside the pipeline. If you wanted to know more about the component you could look at the ObjectType or ComponentClassID properties. After that it gets a bit harder and you should get a reference to the wrapper object as the comment suggest and start using the properties, just like you would in the create packages samples, see our Code Development category for some for these examples. Download Sample code project PackageObjects.zip (5KB)

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• “Query cost (relative to the batch)” <> Query cost relative to batch

  - by Dave Ballantyne

  OK, so that is quite a contradictory title, but unfortunately it is true that a common misconception is that the query with the highest percentage relative to batch is the worst performing.  Simply put, it is a lie, or more accurately we dont understand what these figures mean. Consider the two below simple queries: SELECT * FROM Person.BusinessEntity JOIN Person.BusinessEntityAddress ON Person.BusinessEntity.BusinessEntityID = Person.BusinessEntityAddress.BusinessEntityID go SELECT * FROM Sales.SalesOrderDetail JOIN Sales.SalesOrderHeader ON Sales.SalesOrderDetail.SalesOrderID = Sales.SalesOrderHeader.SalesOrderID After executing these and looking at the plans, I see this : So, a 13% / 87% split ,  but 13% / 87% of WHAT ? CPU ? Duration ? Reads ? Writes ? or some magical weighted algorithm ?  In a Profiler trace of the two we can find the metrics we are interested in. CPU and duration are well out but what about reads (210 and 1935)? To save you doing the maths, though you are more than welcome to, that’s a 90.2% / 9.8% split.  Close, but no cigar. Lets try a different tact.  Looking at the execution plan the “Estimated Subtree cost” of query 1 is 0.29449 and query 2 its 1.96596.  Again to save you the maths that works out to 13.03% and 86.97%, round those and thats the figures we are after.  But, what is the worrying word there ? “Estimated”.  So these are not “actual”  execution costs,  but what’s the problem in comparing the estimated costs to derive a meaning of “Most Costly”.  Well, in the case of simple queries such as the above , probably not a lot.  In more complicated queries , a fair bit. By modifying the second query to also show the total number of lines on each order SELECT *,COUNT(*) OVER (PARTITION BY Sales.SalesOrderDetail.SalesOrderID) FROM Sales.SalesOrderDetail JOIN Sales.SalesOrderHeader ON Sales.SalesOrderDetail.SalesOrderID = Sales.SalesOrderHeader.SalesOrderID The split in percentages is now 6% / 94% and the profiler metrics are : Even more of a discrepancy. Estimates can be out with actuals for a whole host of reasons,  scalar UDF’s are a particular bug bear of mine and in-fact the cost of a udf call is entirely hidden inside the execution plan.  It always estimates to 0 (well, a very small number). Take for instance the following udf Create Function dbo.udfSumSalesForCustomer(@CustomerId integer) returns money as begin Declare @Sum money Select @Sum= SUM(SalesOrderHeader.TotalDue) from Sales.SalesOrderHeader where CustomerID = @CustomerId return @Sum end If we have two statements , one that fires the udf and another that doesn't: Select CustomerID from Sales.Customer order by CustomerID go Select CustomerID,dbo.udfSumSalesForCustomer(Customer.CustomerID) from Sales.Customer order by CustomerID The costs relative to batch is a 50/50 split, but the has to be an actual cost of firing the udf. Indeed profiler shows us : No where even remotely near 50/50!!!! Moving forward to window framing functionality in SQL Server 2012 the optimizer sees ROWS and RANGE ( see here for their functional differences) as the same ‘cost’ too SELECT SalesOrderDetailID,SalesOrderId, SUM(LineTotal) OVER(PARTITION BY salesorderid ORDER BY Salesorderdetailid RANGE unbounded preceding) from Sales.SalesOrderdetail go SELECT SalesOrderDetailID,SalesOrderId, SUM(LineTotal) OVER(PARTITION BY salesorderid ORDER BY Salesorderdetailid Rows unbounded preceding) from Sales.SalesOrderdetail By now it wont be a great display to show you the Profiler trace reads a *tiny* bit different. So moral of the story, Percentage relative to batch can give a rough ‘finger in the air’ measurement, but dont rely on it as fact.

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• My new laptop - with a really nice battery option

  - by Rob Farley

  It was about time I got a new laptop, and so I made a phone-call to Dell to discuss my options. I decided not to get an SSD from them, because I’d rather choose one myself – the sales guy tells me that changing the HD doesn’t void my warranty, so that’s good (incidentally, I’d love to hear people’s recommendations for which SSD to get for my laptop). Unfortunately this machine only has one HD slot, but I figure that I’ll put lots of stuff onto external disks anyway. The machine I got was a Dell Studio XPS 16. It’s red (which suits my company), but also has the Intel® Core™ i7-820QM Processor, which is 4 Cores/8 Threads. Makes for a pretty Task Manager, but nothing like the one I saw at SQLBits last year (at 96 cores), or the one that my good friend James Rowland-Jones writes about here. But the reason for this post is actually something in the software that comes with the machine – you know, the stuff that most people uninstall at the earliest opportunity. I had just reinstalled the operating system, and was going through the utilities to get the drivers up-to-date, when I noticed that one of Dell applications included an option to disable battery charging. So I installed it. And sure enough, I can tell the battery not to charge now. Clearly Dell see it as a temporary option, and one that’s designed for when you’re on a plane. But for me, I most often use my laptop with the power plugged in, which means I don’t need to have my battery continually topping itself up. So I really love this option, but I feel like it could go a little further. I’d like “Not Charging” to be the default option, and let me set it when I want to charge it (which should theoretically make my battery last longer). I also intend to work out how this option works, so that I can script it and put it into my StartUp options (so it can be the Default setting). Actually – if someone has already worked this out and can tell me what it does, then please feel free to let me know. Even better would be an external switch. I had a switch on my old laptop (a Dell Latitude) for WiFi, so that I could turn that off before I turned on the computer (this laptop doesn’t give me that option – no physical switch for flight mode). I guess it just means I’ll get used to leaving the WiFi off by default, and turning it on when I want it – might save myself some battery power that way too. Soon I’ll need to take the plunge and sync my iPhone with the new laptop. I’m a little worried that I might lose something – Apple’s messages about how my stuff will be wiped and replaced with what’s on the PC doesn’t fill me with confidence, as it’s a new PC that doesn’t have stuff on it. But having a new machine is definitely a nice experience, and one that I can recommend. I’m sure when I get around to buying an SSD I’ll feel like it’s shiny and new all over again! Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Four New Java Champions

  - by Tori Wieldt

  Four luminaries in the Java community have been selected as new Java Champions. The are Agnes Crepet, Lars Vogel, Yara Senger and Martijn Verburg. They were selected for their technical knowledge, leadership, inspiration, and tireless work for the community. Here is how they rock the Java world: Agnes Crepet Agnes Crepet (France) is a passionate technologist with over 11 years of software engineering experience, especially in the Java technologies, as a Developer, Architect, Consultant and Trainer. She has been using Java since 1999, implementing multiple kinds of applications (from 20 days to 10000 men days) for different business fields (banking, retail, and pharmacy). Currently she is a Java EE Architect for a French pharmaceutical company, the homeopathy world leader. She is also the co-founder, with other passionate Java developers, of a software company named Ninja Squad, dedicated to Software Craftsmanship. Agnes is the leader of two Java User Groups (JUG), the Lyon JUG Duchess France and the founder of the Mix-IT Conferenceand theCast-IT Podcast, two projects about Java and Agile Development. She speaks at Java and JUG conferences around the world and regularly writes articles about the Java Ecosystem for the French print Developer magazine Programmez! and for the Duchess Blog. Follow Agnes @agnes_crepet. Lars Vogel Lars Vogel (Germany) is the founder and CEO of the vogella GmbH and works as Java, Eclipse and Android consultant, trainer and book author. He is a regular speaker at international conferences, such as EclipseCon, Devoxx, Droidcon and O'Reilly's Android Open. With more than one million visitors per month, his website vogella.com is one of the central sources for Java, Eclipse and Android programming information. Lars is committer in the Eclipse project and received in 2010 the "Eclipse Top Contributor Award" and 2012 the "Eclipse Top Newcomer Evangelist Award." Follow Lars on Twitter @vogella. Yara Senger Yara Senger (Brazil) has been a tireless Java activist in Brazil for many years. She is President of SouJava and she is an alternate representative of the group on the JCP Executive Committee. Yara has led SouJava in many initiatives, from technical events to social activities. She is co-founder and director of GlobalCode, which trains developers throughout Brazil.  Last year, she was recipient of the Duke Choice's Award, for the JHome embedded environment.  Yara is also an active speaker, giving presentations in many countries, including JavaOne SF, JavaOne Latin Ameria, JavaOne India, JFokus, and JUGs throughout Brazil. Yara is editor of InfoQ Brasil and also frequently posts at http://blog.globalcode.com.br/search/label/Yara. Follow Yara @YaraSenger. Martijn Verburg Martijn Verburg (UK) is the CTO of jClarity (a Java/JVM performance cloud tooling start-up) and has over 12 years experience as a Java/JVM technology professional and OSS mentor in a variety of organisations from start-ups to large enterprises. He is the co-leader of the London Java Community (~2800 developers) and leads the global effort for the Java User Group "Adopt a JSR" and "Adopt OpenJDK" programmes. These programmes encourage day to day Java developer involvement with OpenJDK, Java standards (JSRs), an important relationship for keeping the Java ecosystem relevant to the 9 million Java developers out there today. As a leading expert on technical team optimisation, his talks and presentations are in high demand by major conferences (JavaOne, Devoxx, OSCON, QCon) where you'll often find him challenging the industry status quo via his alter ego "The Diabolical Developer." You can read more in the OTN ariticle "Challenging the Diabolical Developer: A Conversation with JavaOne Rock Star Martijn Verburg." Follow Martijn @karianna. The Java Champions are an exclusive group of passionate Java technology and community leaders who are community-nominated and selected under a project sponsored by Oracle. Java Champions get the opportunity to provide feedback, ideas, and direction that will help Oracle grow the Java Platform. Congratulations to these new Java Champions!

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• ASP.NET MVC: Simple view to display contents of DataTable

  - by DigiMortal

  In one of my current projects I have to show reports based on SQL Server views. My code should be not aware of data it shows. It just asks data from view and displays it user. As WebGrid didn’t seem to work with DataTable (at least with no hocus-pocus) I wrote my own very simple view that shows contents of DataTable. I don’t focus right now on data querying questions as this part of my simple generic reporting stuff is still under construction. If the final result is something good enough to share with wider audience I will blog about it for sure. My view uses DataTable as model. It iterates through columns collection to get column names and then iterates through rows and writes out values of all columns. Nothing special, just simple generic view for DataTable. @model System.Data.DataTable @using System.Data; <h2>Report</h2> <table>     <thead>     <tr>     @foreach (DataColumn col in Model.Columns)         {                  <th>@col.ColumnName</th>     }         </tr>     </thead>             <tbody>     @foreach (DataRow row in Model.Rows)         {                 <tr>         @foreach (DataColumn col in Model.Columns)                 {                          <td>@row[col.ColumnName]</td>         }                 </tr>     }         </tbody> </table> In my controller action I have code like this. GetParams() is simple function that reads parameter values from form. This part of my simple reporting system is still under construction but as you can see it will be easy to use for UI developers. public ActionResult TasksByProjectReport() {      var data = _reportService.GetReportData("MEMOS",GetParams());      return View(data); } Before seeing next silver bullet in this example please calm down. It is just plain and simple stuff for simple needs. If you need advanced and powerful reporting system then better use existing components by some vendor.

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• July, the 31 Days of SQL Server DMO’s – Day 19 (sys.dm_exec_query_stats)

  - by Tamarick Hill

  The sys.dm_exec_query_stats DMV is one of the most useful DMV’s out there when it comes to performance tuning. If you have been keeping up with this blog series this month, you know that I started out on Day 1 reviewing many of the DMV’s within the ‘exec’ namespace. I’m not sure how I missed this one considering how valuable it is, but hey, they say it’s better late than never right?? On Day 7 and Day 8 we reviewed the sys.dm_exec_procedure_stats and sys.dm_exec_trigger_stats respectively. This sys.dm_exec_query_stats DMV is very similar to these two. As a matter of fact, this DMV will return all of the information you saw in the other two DMV’s, but in addition to that, you can see stats for all queries that have cached execution plans on your server. You can even see stats for statements that are ran Ad-Hoc as long as they are still cached in the buffer pool. To better illustrate this DMV, let have a quick look at it: SELECT * FROM sys.dm_exec_query_stats As you can see, there is a lot of information returned from this DMV. I wont go into detail about each and every one of these columns, but I will touch on a few of them briefly. The first column is the ‘sql_handle’, which if you remember from Day 4 of our blog series, I explained how you can use this column to extract the actual SQL text that was executed. The next columns statement_start_offset and statement_end_offset provide you a way of extracting the exact SQL statement that was executed as part of a batch. The plan_handle column is used to extract the Execution plan that was used, which we talked about during Day 5 of this blog series. Later in the result set, you have columns to identify how many times a particular statement was executed, how much CPU time it used, how many reads/writes it performed, the duration, how many rows were returned, etc. These columns provide you with a solid avenue to begin your performance optimization. The last column I will touch on is the query_plan_hash column. A lot of times when you have Dynamic SQL running on your server, you have similar statements with different parameter values being passed in. Many times these types of statements will get similar execution plans and then a Binary hash value can be generated based on these similar plans. This query plan hash can be used to find the cost of all queries that have similar execution plans and then you can tune based on that plan to improve the performance of all of the individual queries. This is a very powerful way of identifying and tuning Ad-hoc statements that run on your server. As I stated earlier, this sys.dm_exec_query_stats DMV is a very powerful and recommended DMV for performance tuning. You are able to quickly identify statements that are running on your server and analyze their impact on system resources. Using this DMV to track down the biggest performance killers on your server will allow you to make the biggest gains once you focus your tuning efforts on those top offenders. For more information about this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms189741.aspx Follow me on Twitter @PrimeTimeDBA

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• Exploring packages in code

  In my previous post Searching for tasks with code you can see how to explore the control flow side of packages, drilling down through containers, task, and event handlers, but it didn’t cover the data flow. I recently saw a post on the MSDN forum asking how to edit an existing package programmatically, and the sticking point was how to find the the data flow and the components inside. This post builds on some of the previous code and shows how you can explore all objects inside a package. I took the sample Task Search application I’d written previously, and came up with a totally pointless little console application that just walks through the package and writes out the basic type and name of every object it finds, starting with the package itself e.g. Package – MyPackage . The sample package we used last time showed nested objects as well an event handler; a OnPreExecute event tucked away on the task SQL In FEL. The output of this sample tool would look like this: PackageObjects v1.0.0.0 (1.0.0.26627) Copyright (C) 2009 Konesans Ltd Processing File - Z:\Users\Darren Green\Documents\Visual Studio 2005\Projects\SSISTestProject\EventsAndContainersWithExe cSQLForSearch.dtsx Package - EventsAndContainersWithExecSQLForSearch For Loop - FOR Counter Loop Task - SQL In Counter Loop Sequence Container - SEQ For Each Loop Wrapper For Each Loop - FEL Simple Loop Task - SQL In FEL Task - SQL On Pre Execute for FEL SQL Task Sequence Container - SEQ Top Level Sequence Container - SEQ Nested Lvl 1 Sequence Container - SEQ Nested Lvl 2 Task - SQL In Nested Lvl 2 Task - SQL In Nested Lvl 1 #1 Task - SQL In Nested Lvl 1 #2 Connection Manager – LocalHost The code is very similar to what we had previously, but there are a couple of extra bits to deal with connections and to look more closely at a task and see if it is a Data Flow task. For connections your just examine the package's Connections collection as shown in the abridged snippets below. First you can see the call to the ProcessConnections method, followed by the method itself. // Load the package file Application application = new Application(); using (Package package = application.LoadPackage(filename, null)) { // Write out the package name Console.WriteLine("Package - {0}", package.Name); ... More ... // Look and the connections ProcessConnections(package.Connections); } private static void ProcessConnections(Connections connections) { foreach (ConnectionManager connectionManager in connections) { Console.WriteLine("Connection Manager - {0}", connectionManager.Name); } } What we didn’t see in the sample output above was anything to do with the Data Flow, but rest assured the code now handles it too. The following snippet shows how each task is examined to see if it is a Data Flow task, and if so we can then loop through all of the components inside the data flow. private static void ProcessTaskHost(TaskHost taskHost) { if (taskHost == null) { return; } Console.WriteLine("Task - {0}", taskHost.Name); // Check if the task is a Data Flow task MainPipe pipeline = taskHost.InnerObject as MainPipe; if (pipeline != null) { ProcessPipeline(pipeline); } } private static void ProcessPipeline(MainPipe pipeline) { foreach (IDTSComponentMetaData90 componentMetadata in pipeline.ComponentMetaDataCollection) { Console.WriteLine("Pipeline Component - {0}", componentMetadata.Name); // If you wish to make changes to the component then you should really use the managed wrapper. // CManagedComponentWrapper wrapper = componentMetadata.Instantiate(); // wrapper.SetComponentProperty("PropertyName", "Value"); } } Hopefully you can see how we get a reference to the Data Flow task, and then use the ComponentMetaDataCollection to find out what components we have inside the pipeline. If you wanted to know more about the component you could look at the ObjectType or ComponentClassID properties. After that it gets a bit harder and you should get a reference to the wrapper object as the comment suggest and start using the properties, just like you would in the create packages samples, see our Code Development category for some for these examples. Download Sample code project PackageObjects.zip (5KB)

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• How do I implement a quaternion based camera?

  - by kudor gyozo

  I looked at several tutorials about this and when I thought I understood I tried to implement a quaternion based camera. The problem is it doesn't work correctly, after rotating for approx. 10 degrees it jumps back to -10 degrees. I have no idea what's wrong. I'm using openTK and it already has a quaternion class. I'm a noob at opengl, I'm doing this just for fun, and don't really understand quaternions, so probably I'm doing something stupid here. Here is some code: (Actually almost all the code except the methods that load and draw a vbo (it is taken from an OpenTK sample that demonstrates vbo-s)) I load a cube into a vbo and initialize the quaternion for the camera protected override void OnLoad(EventArgs e) { base.OnLoad(e); cameraPos = new Vector3(0, 0, 7); cameraRot = Quaternion.FromAxisAngle(new Vector3(0,0,-1), 0); GL.ClearColor(System.Drawing.Color.MidnightBlue); GL.Enable(EnableCap.DepthTest); vbo = LoadVBO(CubeVertices, CubeElements); } I load a perspective projection here. This is loaded at the beginning and every time I resize the window. protected override void OnResize(EventArgs e) { base.OnResize(e); GL.Viewport(0, 0, Width, Height); float aspect_ratio = Width / (float)Height; Matrix4 perpective = Matrix4.CreatePerspectiveFieldOfView(MathHelper.PiOver4, aspect_ratio, 1, 64); GL.MatrixMode(MatrixMode.Projection); GL.LoadMatrix(ref perpective); } Here I get the last rotation value and create a new quaternion that represents only the last rotation and multiply it with the camera quaternion. After this I transform this into axis-angle so that opengl can use it. (This is how I understood it from several online quaternion tutorials) protected override void OnRenderFrame(FrameEventArgs e) { base.OnRenderFrame(e); GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit); double speed = 1; double rx = 0, ry = 0; if (Keyboard[Key.A]) { ry = -speed * e.Time; } if (Keyboard[Key.D]) { ry = +speed * e.Time; } if (Keyboard[Key.W]) { rx = +speed * e.Time; } if (Keyboard[Key.S]) { rx = -speed * e.Time; } Quaternion tmpQuat = Quaternion.FromAxisAngle(new Vector3(0,1,0), (float)ry); cameraRot = tmpQuat * cameraRot; cameraRot.Normalize(); GL.MatrixMode(MatrixMode.Modelview); GL.LoadIdentity(); Vector3 axis; float angle; cameraRot.ToAxisAngle(out axis, out angle); GL.Rotate(angle, axis); GL.Translate(-cameraPos); Draw(vbo); SwapBuffers(); } Here are 2 images to explain better: I rotate a while and from this: it jumps into this Any help is appreciated. Update1: I add these to a streamwriter that writes into a file: sw.WriteLine("camerarot: X:{0} Y:{1} Z:{2} W:{3} L:{4}", cameraRot.X, cameraRot.Y, cameraRot.Z, cameraRot.W, cameraRot.Length); sw.WriteLine("ry: {0}", ry); The log is available here: http://www.pasteall.org/26133/text. At line 770 the cube jumps from right to left, when camerarot.Y changes signs. I don't know if this is normal. Update2 Here is the complete project.

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• F# in ASP.NET, mathematics and testing

  - by DigiMortal

  Starting from Visual Studio 2010 F# is full member of .NET Framework languages family. It is functional language with syntax specific to functional languages but I think it is time for us also notice and study functional languages. In this posting I will show you some examples about cool things other people have done using F#. F# and ASP.NET As I am ASP/ASP.NET MVP I am – of course – interested in how people use different languages and technologies with ASP.NET. C# MVP Tomáš Petrícek writes about developing ASP.NET MVC applications using F#. He also shows how to use LINQ To SQL in F# (using F# PowerPack) and provides sample solution and Visual Studio 2010 template for F# MVC web applications. You may also find interesting how you can create controllers in F#. Excellent work, Tomáš! Vladimir Matveev has interesting example about how to use F# and ApplicationHost class to process ASP.NET requests ouside of IIS. This is simple and very straight-forward example and I strongly suggest you to take a look at it. Very cool example is project Strom in Codeplex. Storm is web services testing tool that is fully written on F#. Take a look at this site because Codeplex offers also source code besides binaries. Math Functional languages are strong in fields like mathematics and physics. When I wrote my C# example about BigInteger class I found out that recursive version of Fibonacci algorithm in C# is not performing well. In same time I made same experiment on F# and in F# there were no performance problems with recursive version. You can find F# version of Fibonacci algorithm from Bob Palmer’s blog posting Fibonacci numbers in F#. Although golden spiral is useful for solving many problems I looked for some practical code example and found one. Kean Walmsley published in his Through the Interface blog very interesting posting Creating Fibonacci spirals in AutoCAD using F#. There are also other cool examples you may be interested in. Using numerical components by Extreme Optimization  it is possible to make some numerical integration (quadrature method) using F# (also C# example is available). fsharp.it introduces factorials calculation on F#. Robert Pickering has made very good work on programming The Game of Life in Silverlight and F# – I definitely suggest you to try out this example as it is very illustrative too. Who wants something more complex may take a look at Newton basin fractal example in F# by Jonathan Birge. Testing After some searching and surfing I found out that there is almost everything available for F# to write tests and test your F# code. FsCheck - FsCheck is a port of Haskell's QuickCheck. Important parts of the manual for using FsCheck is almost literally "adapted" from the QuickCheck manual and paper. Any errors and omissions are entirely my responsibility. FsTest - This project is designed to Language Oriented Programming constructs around unit testing and behavior testing in F#. The goal of this project is to create a Domain Specific Language for testing F# code in a way that makes sense for functional programming. FsUnit - FsUnit makes unit-testing with F# more enjoyable. It adds a special syntax to your favorite .NET testing framework. xUnit.NET - xUnit.net is a developer testing framework, built to support Test Driven Development, with a design goal of extreme simplicity and alignment with framework features. It is compatible with .NET Framework 2.0 and later, and offers several runners: console, GUI, MSBuild, and Visual Studio integration via TestDriven.net, CodeRush Test Runner and Resharper. It also offers test project integration for ASP.NET MVC. Getting started Well, as a first thing you need Visual Studio 2010. Then take a look at these resources: F# samples @ MSDN Microsoft F# Developer Center @ MSDN F# Language Reference @ MSDN F# blog F# forums Real World Functional Programming: With Examples in F# and C# (Amazon) Happy F#-ing! :)

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• Silverlight Cream for January 04, 2011 -- #1022

  - by Dave Campbell

  In this Issue: Dennis Doomen, Doug Holland, Kunal Chowdhury, Sacha Barber, Paul Sheriff, Mike Snow(-2-), Peter Kuhn(-2-), and Mike Ormond. Above the Fold: Silverlight: "Silverlight: Fixing the BookShelf Sample" Peter Kuhn WP7: "Searching the Windows Phone 7 Marketplace Programmatically" Doug Holland Prism/Cinch: "PRISM 4 Custom Transitioning Region" Sacha Barber Shoutouts: Sacha Barber the author of Cinch asks for some advice from users: Cinch V2 : Question For The Reader Michael Crump introduces us to SnippetManager as a way to organize your Silverlight snippets... I'm thinking any snippet: A better way to organize your Silverlight Code Snippets. Andy Beaulieu announced an update of Physics Helper 4.2 using Farseer 3.2 ... check out the breaking changes though! Dennis Doomen blogged about a new release of his Fluent Assertions: A new year with a new release of Fluent Assertions, with a blog post about it below From SilverlightCream.com: Verifying PropertyChanged events in Silverlight using Fluent Assertions Dennis Doomen release his latest Fluent Assertions for .NET and Silverlight and wrote up a big post about the new event monitoring syntax. Searching the Windows Phone 7 Marketplace Programmatically Doug Holland has a post up on MSDN blogs talking about searching the WP7 Marketplace programmatically... ya know you should be able to do it... here's how. Beginners Guide to Visual Studio LightSwitch (Part - 5) Kunal Chowdhury has Part 5 of a tutorial series on Lightswitch up at SilverlightShow... working with custom validation this time, and for the first time in this series so far actually writes some code! PRISM 4 Custom Transitioning Region Sacha Barber took time to look at Prism4/MEF and Cinch2 and found things to be fine then wrote a custom PRISM region adaptor that uses a TransitionalElement from the Microsoft Transitionals project... code available, blog post to come. Get Application Title from Windows Phone Paul Sheriff has a cool chunk of code up... getting the Application's title programmatically... and other attributes as well, if you were wondering why you might wanna do that. Detecting Users Win7 Mobile Theme Color Mike Snow has a couple as well... first up is how to detect your user's theme... obviously useful if you wanna match it. Selecting an Item in a ComboBox after Adding Items Second for Mike Snow is a general Silverlight issue... setting the selected item on a ComboBox after filling it... if you haven't stumbled across this yet, you will... A Simplified Grid Markup Reloaded Peter Kuhn has a pair of posts up since last time... this first is an extension of Colin Eberhardt's simplified Grid markup system, but it's only useful if you don't plan on using Blend... can we get a show of hands? :) Silverlight: Fixing the BookShelf Sample Next Peter Kuhn has some changes to the Bookshelf code, but more importantly has some excelling tips about shader effects, Effects on Visual Elements and how to make best use of all the above. Displaying HTML Content in Windows Phone 7 Mike Ormond has a WP7 post up describing problems a customer had early on displaying rich text and an attempt to use the WebBrowser control to pull it off and the problems that caused... check out the resultant code, and read the comments as well. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• SQLAuthority News – Monthly list of Puzzles and Solutions on SQLAuthority.com

  - by pinaldave

  This month has been very interesting month for SQLAuthority.com we had multiple and various puzzles which everybody participated and lots of interesting conversation which we have shared. Let us start in latest puzzles and continue going down. There are few answers also posted on facebook as well. SQL SERVER – Puzzle Involving NULL – Resolve – Error – Operand data type void type is invalid for sum operator This puzzle involves NULL and throws an error. The challenge is to resolve the error. There are multiple ways to resolve this error. Readers has contributed various methods. Few of them even have supplied the answer why this error is showing up. NULL are very important part of the database and if one of the column has NULL the result can be totally different than the one expected. SQL SERVER – T-SQL Scripts to Find Maximum between Two Numbers I modified script provided by friend to find greatest number between two number. My script has small bug in it. However, lots of readers have suggested better scripts. Madhivanan has written blog post on the subject over here. SQL SERVER – BI Quiz Hint – Performance Tuning Cubes – Hints This quiz is hosted on my friend Jacob‘s site. I have written many hints how one can tune cubes. Now one can take part here and win exciting prizes. SQL SERVER – Solution – Generating Zero Without using Any Numbers in T-SQL Madhivanan has asked very interesting question on his blog about How to Generate Zero without using Any Numbers in T-SQL. He has demonstrated various methods how one can generate Zero. I asked the same question on blog and got many interesting answers which I have shared. SQL SERVER – Solution – Puzzle – Statistics are not Updated but are Created Once I have to accept that this was most difficult puzzle. In this puzzle I have asked even though settings are correct, why statistics of the tables are not getting updated. In this puzzle one is tested with various concepts 1) Indexes, 2) Statistics, 3) database settings etc. There are multiple ways of solving this puzzles. It was interesting as many took interest but only few got it right. SQL SERVER – Question to You – When to use Function and When to use Stored Procedure This is rather straight forward question and not the typical puzzle. The answers from readers are great however, still there is chance of more detailed answers. SQL SERVER – Selecting Domain from Email Address I wrote on selecting domains from email addresses. Madhivanan makes puzzle out of a simple question. He wrote a follow-up post over here. In his post he writes various way how one can find email addresses from list of domains. Well, this is not a puzzle but amazing Guest Post by Feodor Georgiev who has written on subject Job Interviewing the Right Way (and for the Right Reasons). An article which everyone should read. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• Silverlight Cream for February 13, 2011 -- #1046

  - by Dave Campbell

  In this Issue: Loek van den Ouweland, Colin Eberhardt, Rudi Grobler, Joost van Schaik, Mike Taulty(-2-, -3-), Deborah Kurata, David Kelley, Peter Foot, Samuel Jack(-2-), and WindowsPhoneGeek(-2-). Above the Fold: Silverlight: "Silverlight Simple MVVM Commanding" Deborah Kurata WP7: "WP7 CustomInputPrompt control with Cancel button" WindowsPhoneGeek Expression Blend: "Silverlight Templated Image Button with two images" Loek van den Ouweland Shoutouts: Dave Campbell posted a write-up about the project he's on and the use of Sterling: Sterling Object-Oriented Database for ISO 1.0 Released!... Also see Jeremy Likness' post on the 1.0 release: Sterling Object-Oriented Database 1.0 RTM Not necessarily Silverlight, but darn cool, a great control by Sasha Barber: WPF : A Weird 3d based control snoutholder announced new content: Windows Phone 7 QuickStarts Live! From SilverlightCream.com: Silverlight Templated Image Button with two images Loek van den Ouweland has a video tutorial up for creating an ImageButton with a hover state... Expression Blend coolness, and check out the external links he has to their training site. Windows Phone 7 Performance Measurements – Emulator vs. Hardware Colin Eberhardt's latest is a popular post comparing performance metrics between the WP7 emulator and a real device. Mileage may vary, but I'm pretty sure the overall results are conculsive, and should help the way you view your app as you're building in the emulator. WP7: WebClient vs HttpWebRequest Rudi Grobler's latest is a discussion of WebClient and HttpWebRequest, gives coding examples of each plus discussion of why you may choose one over the other... and pay attention to his comment about mobile providers. A Blendable Windows Phone 7 / Silverlight clipping behavior Joost van Schaik posted this WP7/Silverlight clipping behavior he developed because all the other solutions were not blendable. Another really useful piece of code from Joost! Blend Bits 22–Being Stylish Mike Taulty has 3 more episodes in his Blend Bits series... first up is on one Styles... explicit, implicit, inheriting... you name it, he's covering it! Blend Bits 23–Templating Part 1 MIke Taulty then has the beginning of a series within his Blend Bits series on Templating. This is something you just have to either bite the bullet and go with Blend to do, or consume someone else's work. Mike shows us how to do it ourself by tweaking the visual aspects of a checkbox Blend Bits 24–Templating Part 2 In part 2 of the Templating series, Mike Taulty digs deeper into Blend and cracks open the Listbox control to take a bunch of the inner elements out for a spin... fun stuff and great tutorial, Mike! Silverlight Simple MVVM Commanding Deborah Kurata has another great MVVM post up... if you don't have your head wrapped around commanding yet, this is a good place to start that process... VB and C# as always. App Development for Windows Phone 7 101 David Kelley goes through the basics of producing a WP7 app both from the Silverlight and XNA side... good info and good external links to get you going. Copyable TextBlock for Windows Phone Peter Foot takes a look at the Copy/Paste functionality in WP7 and how to apply it to a TextBlock... which is NOT an out-of-the-box solution. How to deploy to, and debug, multiple instances of the Windows Phone 7 emulator Samuel Jack has a couple posts up this week... first is this clever one on running multiple copies of the emulator at once... too cool for debugging a multi-player game! Multi-player enabling my Windows Phone 7 game: Day 3 – The Server Side Samuel Jack's latest is a detailed look at his day 3 adventure of taking his multi-player game to WP7... lots of information and external links... what do you say, give him another day? :) WP7 CustomInputPrompt control with Cancel button WindowsPhoneGeek has a couple more posts up... first is this "CustomInputPrompt" control based off the InputPrompt from Coding4Fun. Implementing Windows Phone 7 DataTemplateSelector and CustomDataTemplateSelector In his latest post, WindowsPhoneGeek writes a DataTemplateSelector to allow different data templates for different list elements based on the type of the element. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• MySQL Cluster 7.3: On-Demand Webinar and Q&A Available

  - by Mat Keep

  The on-demand webinar for the MySQL Cluster 7.3 Development Release is now available. You can learn more about the design, implementation and getting started with all of the new MySQL Cluster 7.3 features from the comfort and convenience of your own device, including: - Foreign Key constraints in MySQL Cluster - Node.js NoSQL API  - Auto-installation of higher performance distributed, clusters We received some great questions over the course of the webinar, and I wanted to share those for the benefit of a broader audience. Q. What Foreign Key actions are supported: A. The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL Q. Where are Foreign Keys implemented, ie data nodes or SQL nodes? A. They are implemented in the data nodes, therefore can be enforced for both the SQL and NoSQL APIs Q. Are they compatible with the InnoDB Foreign Key implementation? A. Yes, with the following exceptions: - InnoDB doesn’t support “No Action” constraints, MySQL Cluster does - You can choose to suspend FK constraint enforcement with InnoDB using the FOREIGN_KEY_CHECKS parameter; at the moment, MySQL Cluster ignores that parameter. - You cannot set up FKs between 2 tables where one is stored using MySQL Cluster and the other InnoDB. - You cannot change primary keys through the NDB API which means that the MySQL Server actually has to simulate such operations by deleting and re-adding the row. If the PK in the parent table has a FK constraint on it then this causes non-ideal behaviour. With Restrict or No Action constraints, the change will result in an error. With Cascaded constraints, you’d want the rows in the child table to be updated with the new FK value but, the implicit delete of the row from the parent table would remove the associated rows from the child table and the subsequent implicit insert into the parent wouldn’t reinstate the child rows. For this reason, an attempt to add an ON UPDATE CASCADE where the parent column is a primary key will be rejected. Q. Does adding or dropping Foreign Keys cause downtime due to a schema change? A. Nope, this is an online operation. MySQL Cluster supports a number of on-line schema changes, ie adding and dropping indexes, adding columns, etc. Q. Where can I see an example of node.js with MySQL Cluster? A. Check out the tutorial and download the code from GitHub Q. Can I use the auto-installer to support remote deployments? How about setting up MySQL Cluster 7.2? A. Yes to both! Q. Can I get a demo Check out the tutorial. You can download the code from http://labs.mysql.com/ Go to Select Build drop-down box Q. What is be minimum internet speen required for Geo distributed cluster with synchronous replication? A. if you're splitting you cluster between sites then we recommend a network latency of 20ms or less. Alternatively, use MySQL asynchronous replication where the latency of your WAN doesn't impact the latency of your reads/writes. Q. Where you can one learn more about the PayPal project with MySQL Cluster? A. Take a look at the following - you'll find press coverage, a video and slides from their keynote presentation  So, if you want to learn more, listen to the new MySQL Cluster 7.3 on-demand webinar  MySQL Cluster 7.3 is still in the development phase, so it would be great to get your feedback on these new features, and things you want to see!

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• Agile Manifesto, Revisited

  - by GeekAgilistMercenary

  Again, conversations give me a zillion things to write about.  The recent conversation that has cropped up again is my various viewpoints of the Agile Manifesto.  Not all the processes that came after the manifesto was written, but just the core manifesto itself.  Just for context, here is the manifesto in all the glory. We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value: Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan That is, while there is value in the items on the right, we value the items on the left more. Several of the key signatories at the time went on to write some of the core books that really gave Agile Software Development traction.  If you check out the Agile Manifesto Site and do a search for any of those people, you will find a treasure trove of software development information. My 2 Cents First off, I agree with a few people out there.  Agile is not Scrum for instance.  Do NOT get these things confused when checking out Agile, or pushing forward with Scrum.  As David Starr points out in his blog entry, "About 35 minutes into this discussion, I realized I hadn?t heard a question or comment that wasn?t related to Scrum. I asked the room, ?How many people are on an agile team that is NOT using Scrum?? 5 hands. Seriously, out of about 150 people of so. 5 hands." So know, as this is one of my biggest pet peves these days, that Scrum is not Agile.  Another quote David writes, "I assure you, dear reader, 2 week time boxes does not an agile team make." This is the exact problem.  Take a look at the actual manifesto above.  First ideal, "Individuals and interactions over processes and tools".  There are a couple of meanings in this ideal, just as there are in the other written ideals.  But this one has a lot of contention with a set practice such as Scrum.  There are other formulas, namely XP (eXtreme) and Kanban are two that come to mind often.  But none of these are Agile, but instead a process based on the ideals of Agile. Some of you may be thinking, "that?s the same thing".  Well, no, it is not.  This type of differentiation is vitally important.  Agile is a set of ideals.  Processes are nice, but they can change, they may work for some and not others.  The Agile Manifesto covers the ideals behind what is intended, that intention being to learn and find new ways to build better software. Ideals, not processes.  Definition versus implementation.  Class versus object.  The ideals are of utmost importance, the processes are secondary, the first ideal is what really lays this out for me "Individuals and interactions over processes and tools".  Yes, we need tools but we need the individuals and their interactions more. For those coming into a development team, I hope you take this to mind.  It is of utmost importance that this differentiation is known and fought for.  The second the process becomes more important than the individuals and interactions, the team will effectively lose the advantages of Agile Ideals. This is just one of my first thoughts on the topic of Agile.  I will be writing more in the near future about each of the ideals.  I will make a point to outline more of my thoughts, my opinions, and experience with the ideals of Agile and the various processes that are out there.  Maybe, I may stumble upon something new with the help of my readers?  It would be a grand overture to the ideals I hold. For the original entry, check out my personal blog with other juicy tech tidbits, rants, raves, and the like. Agilist Mercenary

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• Thoughts on Thoughts on TDD

  Brian Harry wrote a post entitled Thoughts on TDD that I thought I was going to let lie, but I find that I need to write a response. I find myself in agreement with Brian on many points in the post, but I disagree with his conclusion. Not surprisingly, I agree with the things that he likes about TDD. Focusing on the usage rather than the implementation is really important, and this is important whether you use TDD or not. And YAGNI was a big theme in my Seven Deadly Sins of Programming series. Now, on to what he doesnt like. He says that he finds it inefficient to have tests that he has to change every time he refactors. Here is where we part company. If you are having to do a lot of test rewriting (say, more than a couple of minutes work to get back to green) *often* when you are refactoring your code, I submit that either you are testing things that you dont need to test (internal details rather than external implementation), your code perhaps isnt as decoupled as it could be, or maybe you need a visit to refactorers anonymous. I also like to refactor like crazy, but as we all know, the huge downside of refactoring is that we often break things. Important things. Subtle things. Which makes refactoring risky. *Unless* we have a set of tests that have great coverage. And TDD (or Example-based Design, which I prefer as a term) gives those to us. Now, I dont know what sort of coverage Brian gets with the unit tests that he writes, but I do know that for the majority of the developers Ive worked with and I count myself in that bucket the coverage of unit tests written afterwards is considerably inferior to the coverage of unit tests that come from TDD. For me, it all comes down to the answer to the following question: How do you ensure that your code works now and will continue to work in the future? Im willing to put up with a little efficiency on the front side to get that benefit later. Its not the writing of the code thats the expensive part, its everything else that comes after. I dont think that stepping through test cases in the debugger gets you what you want. You can verify what the current behavior is, sure, and do it fairly cheaply, but you dont help the guy in the future who doesnt know what conditions were important if he has to change your code. His second part that he doesnt like backing into an architecture (go read to see what he means). Ive certainly had to work with code that was like this before, and its a nightmare the code that nobody wants to touch. But thats not at all the kind of code that you get with TDD, because if youre doing it right youre doing the write a failing tests, make it pass, refactor approach. Now, you may miss some useful refactorings and generalizations for this, but if you do, you can refactor later because you have the tests that make it safe to do so, and your code tends to be easy to refactor because the same things that make code easy to write unit tests for make it easy to refactor. I also think Brian is missing an important point. We arent all as smart as he is. Im reminded a bit of the lesson of Intentional Programming, Charles Simonyis paradigm for making programming easier. I played around with Intentional Programming when it was young, and came to the conclusion that it was a pretty good thing if you were as smart as Simonyi is, but it was pretty much a disaster if you were an average developer. In this case, TDD gives you a way to work your way into a good, flexible, and functional architecture when you dont have somebody of Brians talents to help you out. And thats a good thing.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Silverlight Cream for January 12, 2011 -- #1025

  - by Dave Campbell

  In this Issue: Amyo Kabir, Rob Eisenberg, Doug Rathbone, John Papa, Jeff Blankenburg(-2-), Mike Taulty, Peter Kuhn, Laurent Bugnion, Vangos Pterneas, and Senthil Kumar. Above the Fold: Silverlight: "Silverlight Popup sample" Amyo Kabir WP7: "Navigation in a #WP7 application with MVVM Light" Laurent Bugnion XNA: "XNA for Silverlight developers: Part 0 - Why should I care?" Peter Kuhn Shoutouts: Mohamed Mosallem posted a video of an Expression Blend demo he gave recently: Expression Blend Demo Rob Eisenberg posted the winners of the Caliburn.Micro Contest he was running .. and a nice bunch of swag too! Announcing the Caliburn.Micro Contest Winners! Dan Moyer is a LightSwitch enthusiast and writes Why I Believe Visual Studio LightSwitch will be a Win... good well-thought-out and written take on Lightswitch. From SilverlightCream.com: Silverlight Popup sample Amyo Kabir has a post up that is short on description but long on demo and the code is available... put this in the 'a picture is worth 1,000 words category' :) Caliburn.Micro Soup to Nuts Part 7 - All About Conventions The 7th episode of Rob Eisenberg's tutorial series on Caliburn.Micro is up. This episode about some of the conventions that you get out-of-the-box with Caliburn.Micro, what it'll do for you, and how you can modify the behavior of the convention to suit your own taste/style. Two little tips for working with Silverlight chart DateTime Axes Doug Rathbone has been working with the Toolkit Charts for WP7 and finding it difficult to get the info he needs, and now that he's worked it out... he's sharing... particularly information about DateTimeAxis. Silverlight TV 56: WCF RIA Services and Azure The first Silverlight TV of 2011 was John Papa discussing WCF RIA Services and Azure with Saurabh Plant. What I Learned In WP7 – Issue 14 As usual, Jeff Blankenburg is a couple ahead of me... his Issue 14 is about some panorama trickery... like navigating to a specific place in one, or preventing wrapping. What I Learned In WP7 – Issue 15 In Jeff Blankenburg's latest WP7 post, he's sharing some interesting insight into Trial Mode and app sales... from the standpoint of someone selling apps. Blend Bits 20–Group Into Mike Taulty has Part 20 of his Blend Bits series up. This one is demonstrating grouping, and what all can be accomplished (or not) with grouping in Blend. XNA for Silverlight developers: Part 0 - Why should I care? Peter Kuhn has the beginning of a series on WP7 and XNA up at SilverlightShow... this looks to be a good intro and way to get your head wrapped around XNA on the phone. Navigation in a #WP7 application with MVVM Light Laurent Bugnion discusses WP7 navigation via MVVM Light, resolving many of the communication/navigation complexities you can get involved in without a tool like his. Motion detection in Silverlight Vangos Pterneas has a followup postto the one on facial detection... this one is on Motion Detection in Silverlight. If you've got a webcam hooked up, you can give a demo app a dance via a link he has in the post. Adding ApplicationBar in Windows Phone 7 using Expression Blend Senthil Kumar follows up a post about using VS to add an application bar to a WP7 app with this one using Expression Blend Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• Do we still have a case against the goto statement? [closed]

  - by FredOverflow

  Possible Duplicate: Is it ever worthwhile using goto? In a recent article, Andrew Koenig writes: When asked why goto statements are harmful, most programmers will say something like "because they make programs hard to understand." Press harder, and you may well hear something like "I don't really know, but that's what I was taught." For that reason, I'd like to summarize Dijkstra's arguments. He then shows two program fragments, one without a goto and and one with a goto: if (n < 0) n = 0; Assuming that n is a variable of a built-in numeric type, we know that after this code, n is nonnegative. Suppose we rewrite this fragment: if (n >= 0) goto nonneg; n = 0; nonneg: ; In theory, this rewrite should have the same effect as the original. However, rewriting has changed something important: It has opened the possibility of transferring control to nonneg from anywhere else in the program. I emphasized the part that I don't agree with. Modern languages like C++ do not allow goto to transfer control arbitrarily. Here are two examples: You cannot jump to a label that is defined in a different function. You cannot jump over a variable initialization. Now consider composing your code of tiny functions that adhere to the single responsibility principle: int clamp_to_zero(int n) { if (n >= 0) goto n_is_not_negative: n = 0; n_is_not_negative: return n; } The classic argument against the goto statement is that control could have transferred from anywhere inside your program to the label n_is_not_negative, but this simply is not (and was never) true in C++. If you try it, you will get a compiler error, because labels are scoped. The rest of the program doesn't even see the name n_is_not_negative, so it's just not possible to jump there. This is a static guarantee! Now, I'm not saying that this version is better then the one without the goto, but to make the latter as expressive as the first one, we would at least have to insert a comment, or even better yet, an assertion: int clamp_to_zero(int n) { if (n < 0) n = 0; // n is not negative at this point assert(n >= 0); return n; } Note that you basically get the assertion for free in the goto version, because the condition n >= 0 is already written in line 1, and n = 0; satisfies the condition trivially. But that's just a random observation. It seems to me that "don't use gotos!" is one of those dogmas like "don't use multiple returns!" that stem from a time where the real problem were functions of hundreds or even thousand of lines of code. So, do we still have a case against the goto statement, other than that it is not particularly useful? I haven't written a goto in at least a decade, but it's not like I was running away in terror whenever I encountered one. 1 Ideally, I would like to see a strong and valid argument against gotos that still holds when you adhere to established programming principles for clean code like the SRP. "You can jump anywhere" is not (and has never been) a valid argument in C++, and somehow I don't like teaching stuff that is not true. 1: Also, I have never been able to resurrect even a single velociraptor, no matter how many gotos I tried :(

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