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• exception while creating initial context

  - by Harish

  in thread "main" java.lang.NoClassDefFoundError: weblogic/kernel/KernelStatus at weblogic.jndi.Environment.<clinit>(Environment.java:78) at weblogic.jndi.WLInitialContextFactory.getInitialContext(WLInitialContextFactory.java:117) at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:667) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288) I am getting this exception when I try to create a initial context to hit the weblogic server. This is the code I am trying from eclipse.I have added weblogic.jar and wlclient.jar in the classpath. Hashtable env = new Hashtable(); // WebLogic Server 10.x connection details env.put(Context.INITIAL_CONTEXT_FACTORY, "weblogic.jndi.WLInitialContextFactory" ); env.put(Context.PROVIDER_URL, "t3://localhost:7001"); env.put(Context.SECURITY_PRINCIPAL, "xxxxx"); env.put(Context.SECURITY_CREDENTIALS, "******"); return new InitialContext( env Has anyone faced this issue,How to resolve it?

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• Exception while bamboo is checking for changes in svn

  - by tangens

  While configuring a new test plan in Atlassian bamboo, I get the following exception in the log: Recording error: Unable to detect changes : <projectname> Caused by: org.tmatesoft.svn.core.SVNException: svn: Unrecognized SSL message, plaintext connection? svn: OPTIONS request failed on <repo-path> I tried to access the svn repository by hand and it worked (URL looks like this: https://myrepo.org/path/to/repo). The svn sits behind an apache http server. Both the bamboo server and the svn server are running Debian 4.0. Has anybody seen this error before and can give me a hint how to fix it?

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• Extract data from specific range of cells in multiple worksheet in multiple files.

  - by Michele

  Extract data from specific range of cells(always the same cells) in multiple worksheet in multiple files. 1 file=1 day. I have 6 technicians each day of the week, Monday thru Friday. So, 5 files with 6 worksheets. I have entered specific info in specific cells of every work sheet. The range is constant(the same address in EVERY worksheet in every file.) So, I need a formula to extract and calculate the data in the given range and dump it into another spreadsheet. I can forward an example a file if it will help anyone to answer my question. Or more explanation if necessary is available upon request. JUST PLEASE SOMEBODY HELP ME!!!!! Thank you all in advance. Regards, Michele

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• How can I recover [data from] my failing USB key?

  - by moe37x3

  I have a Corsair Flash Voyager USB key, and it's almost completely failed. When I plug it into my [WinXP] computer, the OS mounts it and open up explorer to the drive's root directory. However, if I try to copy any data off, I get an error message saying that the device is not there. If I leave it plugged in, the OS seems to oscillate between seeing it and not seeing it, since the "Safely Remove Hardware" tray icon appears and disappears every few seconds. The damage was probably caused by my abuse, either from plugging it in with my keys hanging off of it or from losing the cap and keeping it in my pocket uncapped. Is there anything I can do to save the data from it or even rehabilitate the drive?

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• Where to go to see an exception thrown by a browser based java app

  - by vaccano

  I have a java app that is running in my browser. At a specific point the app will crash. I would like to find the exception that is being thrown (if possible) so I can show it to the support of the company that makes the app. Is there a standard place for this? Or a way that capture it? (So I can prove that it is happening.) I am using Firefox, but could use IE if needed.

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• Changing Word mail merge data source locations in bulk?

  - by Daft Viking

  I've just moved a number of Word mail merge files, and a number of Excel spreadsheets that are the data sources for the mail merges, from a Windows XP computer to a Windows 7 computer, and now all the paths for the merge sources are incorrect (used to be c:\documents and settings\user\my documents.... now c:\users\documents....). While I can correct the path of the data source in each file individually, I was hoping that there would be some way of updating the files in bulk, as there are a relatively large number of them. Word 2007 is what is being used, but the documents are all in the previous DOC format (not DOCX).

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• Rest client throw timeout exception

  - by shandu

  Hi, I have create REST client in C# using example on this page: http://msdn.microsoft.com/en-us/library/aa395208(v=vs.90).aspx. Server is built in PHP. When I send request to some urls I have this exception: The request channel timed out while waiting for a reply after 00:00:59.9531250. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout. But, sometimes, when I debug code, I get response. How to solve this?

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• Rest client throw timeout exception

  - by shandu

  Hi, I have create REST client in C# using example on this page: http://msdn.microsoft.com/en-us/library/aa395208(v=vs.90).aspx. Server is built in PHP. When I send request to some urls I have this exception: The request channel timed out while waiting for a reply after 00:00:59.9531250. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout. But, sometimes, when I debug code, I get response. How to solve this?

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• Unknown Exception when entering particular keystrokes in Notepad++

  - by Dwza

  When I enter the keystrokes - in a normla file, everting works fine. When I put in <?php and save the file, use the same keystrokes again, than a unknown exception appears. If i delete <?php and try it again, everything works well again. What could this be ? I searched in the Internet, no results. I tried to reinstall all my plugins, no result. I updated my np++, no result. (On my work I use the same version. It works there!)

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• Does replacing chrome User Data with my own - works without leaving any trace behind? Where else chrome writes data outside of User Data folder?

  - by Selin Peck

  Does replacing chrome User Data with my own - works without leaving any trace behind? Where else chrome writes data outside of User Data folder? I used to start office work by removing chrome User Data, replacing it with my own User Data copied from my external drive, saving the original User Data to other folder. Before leaving in the evening, I will take back my own User Data, and bring back the original User Data where it is originally saved. Is this process advisable? Would I be safe this way or if not, where else does chrome save data outside of User Data folder in AppData? Also, how is the process in Mozilla Firefox?

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• How do I populate multiple records of data into a PDF form like a mail-merge?

  - by user38801

  I have Acrobat Pro, and I have a PDF with a form on it. Assuming the fields in the form correspond to a data source (like rows in an RDBMS table or xml file), I want to then print multiple copies of the PDF file, with each copy having the values of a different row in the data source. It is preferable to directly interface with an actual database, rather than having to save an XML file every time I do this. If this involves programming that's cool too, I only posted here because the question didn't seem appropriate for StackOverflow. Thanks!

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• Is there a data dictionary view that allows one to monitor log usage by Process ID?

  - by ConcernedOfTunbridgeWells

  What (if any) data dictionary views on SQL Server 2005 allow one to monitor log space usage on active queries by Process ID?

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• Ways to improve completeness of files for data recovery and scanning?

  - by SteveO

  I am using R-studio for data recovery on one of my ntfs partition. There is a pdf file about 16MB, but the software can only recover 15MB of it. So I am thinking about what ways can be used to improve the quality of scanning and recovery by the software? I am looking around its preferences. I am not quite sure whether there are some adjustable parameters for scanning and recovery which can be fine-tuned to improve the quality? R-studio has a free demo version, for which scanning is free,but recovery isn't. It is downloadable from http://www.data-recovery-software.net/Data_Recovery_Download.shtml Its manual is here http://www.r-tt.com/downloads/Recovery_Manual.pdf. I have tried my best to search for answers in the manual, but failed to find one. Their technical support is not as good as their software, and helpless usually in my opinion. Thanks!

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• Overflow exception while performing parallel factorization using the .NET Task Parallel Library (TPL

  - by Aviad P.

  Hello, I'm trying to write a not so smart factorization program and trying to do it in parallel using TPL. However, after about 15 minutes of running on a core 2 duo machine, I am getting an aggregate exception with an overflow exception inside it. All the entries in the stack trace are part of the .NET framework, the overflow does not come from my code. Any help would be appreciated in figuring out why this happens. Here's the commented code, hopefully it's simple enough to understand: class Program { static List<Tuple<BigInteger, int>> factors = new List<Tuple<BigInteger, int>>(); static void Main(string[] args) { BigInteger theNumber = BigInteger.Parse( "653872562986528347561038675107510176501827650178351386656875178" + "568165317809518359617865178659815012571026531984659218451608845" + "719856107834513527"); Stopwatch sw = new Stopwatch(); bool isComposite = false; sw.Start(); do { /* Print out the number we are currently working on. */ Console.WriteLine(theNumber); /* Find a factor, stop when at least one is found (using the Any operator). */ isComposite = Range(theNumber) .AsParallel() .Any(x => CheckAndStoreFactor(theNumber, x)); /* Of the factors found, take the one with the lowest base. */ var factor = factors.OrderBy(x => x.Item1).First(); Console.WriteLine(factor); /* Divide the number by the factor. */ theNumber = BigInteger.Divide( theNumber, BigInteger.Pow(factor.Item1, factor.Item2)); /* Clear the discovered factors cache, and keep looking. */ factors.Clear(); } while (isComposite); sw.Stop(); Console.WriteLine(isComposite + " " + sw.Elapsed); } static IEnumerable<BigInteger> Range(BigInteger squareOfTarget) { BigInteger two = BigInteger.Parse("2"); BigInteger element = BigInteger.Parse("3"); while (element * element < squareOfTarget) { yield return element; element = BigInteger.Add(element, two); } } static bool CheckAndStoreFactor(BigInteger candidate, BigInteger factor) { BigInteger remainder, dividend = candidate; int exponent = 0; do { dividend = BigInteger.DivRem(dividend, factor, out remainder); if (remainder.IsZero) { exponent++; } } while (remainder.IsZero); if (exponent > 0) { lock (factors) { factors.Add(Tuple.Create(factor, exponent)); } } return exponent > 0; } } Here's the exception thrown: Unhandled Exception: System.AggregateException: One or more errors occurred. --- > System.OverflowException: Arithmetic operation resulted in an overflow. at System.Linq.Parallel.PartitionedDataSource`1.ContiguousChunkLazyEnumerator.MoveNext(T& currentElement, Int32& currentKey) at System.Linq.Parallel.AnyAllSearchOperator`1.AnyAllSearchOperatorEnumerator`1.MoveNext(Boolean& currentElement, Int32& currentKey) at System.Linq.Parallel.StopAndGoSpoolingTask`2.SpoolingWork() at System.Linq.Parallel.SpoolingTaskBase.Work() at System.Linq.Parallel.QueryTask.BaseWork(Object unused) at System.Linq.Parallel.QueryTask.<.cctor>b__0(Object o) at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.Execute() --- End of inner exception stack trace --- at System.Linq.Parallel.QueryTaskGroupState.QueryEnd(Boolean userInitiatedDispose) at System.Linq.Parallel.SpoolingTask.SpoolStopAndGo[TInputOutput,TIgnoreKey](QueryTaskGroupState groupState, PartitionedStream`2 partitions, SynchronousChannel`1[] channels, TaskScheduler taskScheduler) at System.Linq.Parallel.DefaultMergeHelper`2.System.Linq.Parallel.IMergeHelper<TInputOutput>.Execute() at System.Linq.Parallel.MergeExecutor`1.Execute[TKey](PartitionedStream`2 partitions, Boolean ignoreOutput, ParallelMergeOptions options, TaskScheduler taskScheduler, Boolean isOrdered, CancellationState cancellationState, Int32 queryId) at System.Linq.Parallel.PartitionedStreamMerger`1.Receive[TKey](PartitionedStream`2 partitionedStream) at System.Linq.Parallel.AnyAllSearchOperator`1.WrapPartitionedStream[TKey](PartitionedStream`2 inputStream, IPartitionedStreamRecipient`1 recipient, BooleanpreferStriping, QuerySettings settings) at System.Linq.Parallel.UnaryQueryOperator`2.UnaryQueryOperatorResults.ChildResultsRecipient.Receive[TKey](PartitionedStream`2 inputStream) at System.Linq.Parallel.ScanQueryOperator`1.ScanEnumerableQueryOperatorResults.GivePartitionedStream(IPartitionedStreamRecipient`1 recipient) at System.Linq.Parallel.UnaryQueryOperator`2.UnaryQueryOperatorResults.GivePartitionedStream(IPartitionedStreamRecipient`1 recipient) at System.Linq.Parallel.QueryOperator`1.GetOpenedEnumerator(Nullable`1 mergeOptions, Boolean suppressOrder, Boolean forEffect, QuerySettings querySettings) at System.Linq.Parallel.QueryOpeningEnumerator`1.OpenQuery() at System.Linq.Parallel.QueryOpeningEnumerator`1.MoveNext() at System.Linq.Parallel.AnyAllSearchOperator`1.Aggregate() at System.Linq.ParallelEnumerable.Any[TSource](ParallelQuery`1 source, Func`2 predicate) at PFact.Program.Main(String[] args) in d:\myprojects\PFact\PFact\Program.cs:line 34 Any help would be appreciated. Thanks!

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• Servlet stops without giving any exception

  - by Fahim

  Hi, I have implemented a Servlet hosted on Tomcat 6 server on Mandriva Linux. I have been able to make the client communicate with the Servlet. In response to a request the Servlet tries to instantiate a another class (named KalmanFilter) located in the same directory. The KalmanFilter tries to create four Matrices (using Jama Matrix package). But at this point Servlet stops without giving any exception ! However, from another test code in the same directory I have been able to create instance of KalmanFilter class, and proceed without any error. The problem occurs only when my Servlet tries to instantiate the KalmanFilter class and create the matrices. Any idea? Below are the codes: MyServlet.java import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.*; public class MyServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{ doGet(request, response); } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException{ PrintWriter out = null; //response.getWriter(); try{ System.out.println("creating new KalmanFilter"); KalmanFilter filter = new KalmanFilter(); out = response.getWriter(); out.print("filter created"); }catch(Exception ex){ ex.printStackTrace(); System.out.println("Exception in doGet(): " + ex.getMessage()); ex.printStackTrace(out); } } } KalmanFilter.java import Jama.Matrix; public class KalmanFilter { protected Matrix X, X0; protected Matrix F, Q; //protected Matrix F, B, U, Q; protected Matrix H, R; protected Matrix P, P0; private final double EPSILON = 0.001; public KalmanFilter(){ System.out.println("from constructor of KalmanFilter"); createInitialMatrices(); } private void createInitialMatrices(){ System.out.println("from KalmanFilter.createInitialMatrices()"); double[][] pVals = { {1.0, 0.0}, {0.0, 1.0} }; double[][] qVals = { {EPSILON, EPSILON}, {EPSILON, EPSILON} }; double[][] hVals = { {1.0, 0.0}, {0.0, 1.0}, {1.0, 0.0}, {0.0, 1.0} }; double[][] xVals = { {0.0}, {0.0}, }; System.out.println("creating P Q H X matrices in createInitialMatrices()"); try{ this.P = new Matrix(pVals); System.out.println("created P matrix in createInitialMatrices()"); this.Q = new Matrix(qVals); System.out.println("created Q matrix in createInitialMatrices()"); this.H = new Matrix(hVals); System.out.println("created H matrix in createInitialMatrices()"); this.X = new Matrix(xVals); System.out.println("created X matrix in createInitialMatrices()"); System.out.println("created P Q H X matrices in createInitialMatrices()"); }catch(Exception e){ System.out.println("Exception from createInitialMatrices()"+ e.getMessage()); e.printStackTrace(); } System.out.println("returning from createInitialMatrices()"); } }

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• BadPaddingException in Android encrypt

  - by DarthRoman

  Hi everyone, I am making an Android application, and I want to encrypt a String before sending it to a DataBase, and encrytpion is correct. The problem is when I am going to decrypt the String, because I get a BadPaddingException and I have no idea where the problem is. Here is the code: public final static String HEX = "36A52C8FB7DF9A3F"; public static String encrypt(String seed, String cleartext) throws Exception { byte[] rawKey = getRawKey(seed.getBytes()); byte[] result = encrypt(rawKey, cleartext.getBytes()); return toHex(result); } public static String decrypt(String seed, String encrypted) throws Exception { byte[] rawKey = getRawKey(seed.getBytes()); byte[] enc = toByte(encrypted); byte[] result = decrypt(rawKey, enc); return new String(result); } public static String toHex(String txt) { return toHex(txt.getBytes()); } public static String fromHex(String hex) { return new String(toByte(hex)); } public static byte[] toByte(String hexString) { int len = hexString.length()/2; byte[] result = new byte[len]; for (int i = 0; i < len; i++) result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue(); return result; } public static String toHex(byte[] buf) { if (buf == null) return ""; StringBuffer result = new StringBuffer(2*buf.length); for (int i = 0; i < buf.length; i++) { appendHex(result, buf[i]); } return result.toString(); } private static byte[] getRawKey(byte[] seed) throws Exception { KeyGenerator kgen = KeyGenerator.getInstance("AES"); SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); sr.setSeed(seed); kgen.init(128, sr); // 192 and 256 bits may not be available SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); return raw; } private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception { SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); byte[] encrypted = cipher.doFinal(clear); return encrypted; } private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception { SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.DECRYPT_MODE, skeySpec); byte[] decrypted = cipher.doFinal(encrypted); return decrypted; } private static void appendHex(StringBuffer sb, byte b) { sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f)); } I encrypt and decrypt with this code: String encrypted = encrypt(HEX, "some text"); String decrypted = decrypt(HEX, encrypted); Can anyone help me please? Thank you very much!!

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• Using Microsoft's Chart Controls In An ASP.NET Application: Serializing Chart Data

  In most usage scenarios, the data displayed in a Microsoft Chart control comes from some dynamic source, such as from a database query. The appearance of the chart can be modified dynamically, as well; past installments in this article series showed how to programmatically customize the axes, labels, and other appearance-related settings. However, it is possible to statically define the chart's data and appearance strictly through the control's declarative markup. One of the demos examined in the Getting Started article rendered a column chart with seven columns whose labels and values were defined statically in the <asp:Series> tag's <Points> collection. Given this functionality, it should come as no surprise that the Microsoft Chart Controls also support serialization. Serialization is the process of persisting the state of a control or an object to some other medium, such as to disk. Deserialization is the inverse process, and involves taking the persisted data and recreating the control or object. With just a few lines of code you can persist the appearance settings, the data, or both to a file on disk or to any stream. Likewise, it takes just a few lines of codes to reconstitute a chart from the persisted information. This article shows how to use the Microsoft Chart Control's serialization functionality by examining a demo application that allows users to create custom charts, specifying the data to plot and some appearance-related settings. The user can then save a "snapshot" of this chart, which persists its appearance and data to a record in a database. From another page, users can view these saved chart snapshots. Read on to learn more! Read More >

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• Oracle Database Security Protecting the Oracle IRM Schema

  - by Simon Thorpe

  Acquiring the Information Rights Management technology in 2006 was part of Oracle's strategic security vision and IRM compliments nicely the overall Oracle security set of solutions. A year ago I spoke about how Oracle has solutions that can help companies protect information throughout its entire life cycle. With our acquisition of Sun this set of solutions has solidified and has even extended down to the operating system and hardware level. Oracle can now offer customers technology that protects their data from the disk, through the database to documents on the desktop! With the recent release of Oracle IRM 11g I was tasked to configure demonstration and evaluation environments and I thought it would make a nice story to leverage some of the security features in the latest release of the Oracle Database. After building these environments I thought I would put together a simple video demonstrating how both Database Advanced Security and Information Rights Management combined can provide a very secure platform for protecting your information. Have a look at the following which highlights these database security options.Transparent Data Encryption protecting the communication from the Oracle IRM server to the Database server. Encryption techniques provide confidentiality and integrity of the data passing to and from the IRM service on the back end. Transparent Data Encryption protecting the Oracle IRM database schema. Encryption is used to provide confidentiality of the IRM data whilst it resides at rest in the database table space. Database Vault is used to ensure only the Oracle IRM service has access to query and update the information that resides in the database. This is an excellent method of ensuring that database administrators cannot look at or make changes to the Oracle IRM database whilst retaining their ability to administrate the database. The last thing you want after deploying an IRM solution is for a curious or unhappy DBA to run a query that grants them rights to your company financial data or documents pertaining to a merger or acquisition.

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• Join our webcast: Discover What’s New in Oracle Data Integrator and Oracle GoldenGate

  - by Irem Radzik

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";} Data integration team has organized a series of webcasts for this summer. We are kicking it off this Thursday June 30th at 10am PT with a product update webcast: Discover What’s New in Oracle Data Integrator and Oracle GoldenGate. In this webcast you will hear from product management about the new patch updates to both GoldenGate 11g R1 and ODI 11gR1. Jeff Pollock, Sr. Director of Product Management for ODI will talk about the new features in Oracle Data Integrator 11.1.1.5, including the data lineage integration with OBI EE, enhanced web services to support flexible architectures as well as capabilities for efficient object execution such as Load Plans. Jeff will discuss support for complex files and performance enhancements. Chris McAllister, Sr. Director of Product Management for Oracle GoldenGate will cover the new features of Oracle GoldenGate 11.1.1.1 such as increased data security by supporting Oracle Database Advanced Security option, deeper integration with Oracle Database, and the expanded list of heterogeneous databases GoldenGate supports . Chris will also talk about the new Oracle GoldenGate 11gR1 release for HP NonStop platform and will provide information on our strategic direction for product development. Join us this Thursday at 10am PT/ 1pm ET to hear directly from Data Integration Product Management . You can register here for the June 30th webcast as well as for the upcoming ones in our summer webcast series.

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• SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

  - by pinaldave

  This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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• Methodology behind fetching large XML data sets in pieces

  - by Jerry Dodge

  I am working on an HTTP Server in Delphi which simply sends back a custom XML dataset. I am not following any type of standard formatting, such as SOAP. I have the system working seamlessly, except one small flaw: When I have a very large dataset to send back to the client, it might take up to 2 minutes for all the data to be transferred. The HTTP Server I'm building is essentially an XML Data based API around a database, implementing the common business rule - therefore, the requests are specific to the data behind the system. When, for example, I fetch a large set of product data, I would like to break this down and send it back piece by piece. However, a single HTTP request calls for a single response. I can't necessarily keep feeding the client with multiple different XML packets unless the client explicitly requests it. I don't have any session management, but rather an API Key. I know if I had sessions, I could keep-alive a dataset temporarily for a client, and they could request bits and pieces of it. However, without session management, I would have to execute the SQL query multiple times (for each chunk of data), and in the mean-time, if that data changes, the "pages" might get messed up, therefore causing items to show on the wrong pages, after navigating to a different page. So how is this commonly handled? What's the methodology behind breaking down a large XML dataset into chunks to save the load?

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• Announcing Sesame Data Browser

  - by Fabrice Marguerie

  At the occasion of MIX10, which is currently taking place in Las Vegas, I'd like to announce Sesame Data Browser.Sesame will be a suite of tools for dealing with data, and Sesame Data Browser will be the first tool from that suite.Today, during the second MIX10 keynote, Microsoft demonstrated how they are pushing hard to get OData adopted. If you don't know about OData, you can visit the just revamped dedicated website: http://odata.org. There you'll find about the OData protocol, which allows you to publish and consume data on the web, the OData SDK (with client libraries for .NET, Java, Javascript, PHP, iPhone, and more), a list of OData producers, and a list of OData consumers.This is where Sesame Data Browser comes into play. It's one of the tools you can use today to consume OData.I'll let you have a look, but be aware that this is just a preview and many additional features are coming soon.Sesame Data Browser is part of a bigger picture than just OData that will take shape over the coming months. Sesame is a project I've been working on for many months now, so what you see now is just a start :-)I hope you'll enjoy what you see. Let me know what you think.

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• Using Microsoft's Chart Controls In An ASP.NET Application: Serializing Chart Data

  In most usage scenarios, the data displayed in a Microsoft Chart control comes from some dynamic source, such as from a database query. The appearance of the chart can be modified dynamically, as well; past installments in this article series showed how to programmatically customize the axes, labels, and other appearance-related settings. However, it is possible to statically define the chart's data and appearance strictly through the control's declarative markup. One of the demos examined in the Getting Started article rendered a column chart with seven columns whose labels and values were defined statically in the <asp:Series> tag's <Points> collection. Given this functionality, it should come as no surprise that the Microsoft Chart Controls also support serialization. Serialization is the process of persisting the state of a control or an object to some other medium, such as to disk. Deserialization is the inverse process, and involves taking the persisted data and recreating the control or object. With just a few lines of code you can persist the appearance settings, the data, or both to a file on disk or to any stream. Likewise, it takes just a few lines of codes to reconstitute a chart from the persisted information. This article shows how to use the Microsoft Chart Control's serialization functionality by examining a demo application that allows users to create custom charts, specifying the data to plot and some appearance-related settings. The user can then save a "snapshot" of this chart, which persists its appearance and data to a record in a database. From another page, users can view these saved chart snapshots. Read on to learn more! Read More >

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• “Big Data” Is A Small Concept Unless You Can Apply It To The Customer Experience

  - by Michael Hylton

  There’s been a lot of recent talk in the industry about “big data”.  Much can be said about the importance of big data and the results from it, but you need to always consider the customer experience when analyzing and applying customer data. Personalization and merchandising drive the user experience.  Big data should enable you to gain valuable insight into each of your customers and apply that insight at the moment they are on your Web site, talking to one of your call center agents, or any other touchpoint.  While past customer experience is important, you need to combine that with what your customer is doing on your Web site now as well what they are doing and saying on social networking sites.  It’s key to have a 360 degree view of your customer across all of your touchpoints in order to provide that relevant and consistent experience that they come to expect when interacting with your brand. Big data can enable you to effectively market, merchandize, and recommend the right products to the right customers and the right time.  By taking customer data and applying it to product recommendations, you have an opportunity to gain a greater share of wallet through the cross-selling and up-selling of additional products and services.  You can also build sustaining loyalty programs to continue to engage with your customers throughout their long-term relationship with your brand.

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• “Big Data” Is A Small Concept Unless You Can Apply It To The Customer Experience

  - by Michael Hylton

  There’s been a lot of recent talk in the industry about “big data”.  Much can be said about the importance of big data and the results from it, but you need to always consider the customer experience when analyzing and applying customer data. Personalization and merchandising drive the user experience.  Big data should enable you to gain valuable insight into each of your customers and apply that insight at the moment they are on your Web site, talking to one of your call center agents, or any other touchpoint.  While past customer experience is important, you need to combine that with what your customer is doing on your Web site now as well what they are doing and saying on social networking sites.  It’s key to have a 360 degree view of your customer across all of your touchpoints in order to provide that relevant and consistent experience that they come to expect when interacting with your brand. Big data can enable you to effectively market, merchandize, and recommend the right products to the right customers and the right time.  By taking customer data and applying it to product recommendations, you have an opportunity to gain a greater share of wallet through the cross-selling and up-selling of additional products and services.  You can also build sustaining loyalty programs to continue to engage with your customers throughout their long-term relationship with your brand.

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