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• Is it a bad idea to release software on the night before Christmas?

  - by Conor

  We're about to go live with a new version of our system. It's getting really close to Christmas. I work in a very small company. Everyone will be on leave or sporadically available over the next week or so. I've argued with my boss that this is very risky and that we should go live in the new year when everyone is back and when we can provide full support. He is unflinching - he argues that we need to go live sooner - so that we can get new users and more revenue which we need. The number of new users will be minor amount over the next week or so. There has been a decent amount of system testing performed on the system. However a new live system, in my experience, needs a lot of care and attention in the first few days. Am I being pessimistic or realistic? Update - January: The system did not go live over Christmas. Ongoing system testing revealed various problems. So no support issues to deal with. Still preparing for release...

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• XML DB Content Connector unable to accept binary content due to Invalid argument(s) in call oracle.sql.BLOB.setBinaryStream(0L)

  - by sthieme

  Dear Readers, I am working on implementing a custom Document Management System using the Oracle XML DB Content Connector. See the following documentation link for details Oracle XML DB Developer's Guide 11g Release 2 (11.2)Chapter 31 Using Oracle XML DB Content Connectorhttp://docs.oracle.com/cd/E11882_01/appdev.112/e23094/xdb_jcr.htm especially the following example gave me some trouble to run it successfully Sample Code to Upload Filehttp://docs.oracle.com/cd/E11882_01/appdev.112/e23094/xdb_jcr.htm#ADXDB5627 I had already succeeded to set some of the properties successfully, i.e. jcr:encoding, jcr:mimeType, ojcr:displayName and ojcr:language. However setting the jcr:data property as described in the example failed consistently, both with the documented input FileStream or with a fixed string. contentNode.setProperty("jcr:data", "mystringvalue"); After some research I found the following Support Note which describes the cause for the issue in the JDBC driver version 11.2.0.1. Error "ORA-17068: Invalid argument(s) in call" Using Method setBinaryStream(0L) in JDBC 11.2.0.1 (Doc ID 1234235.1)https://support.oracle.com/epmos/faces/DocContentDisplay?id=1234235.1It can easily be solved by upgrading to JDBC 11.2.0.2 or worked around using the following property setting: java -Doracle.jdbc.LobStreamPosStandardCompliant=false ... Kind regards,Stefan C:\Oracle\Database\product\11.2.0\dbhome_1>java -Doracle.jdbc.LobStreamPosStandardCompliant=false UploadFile jdbc:oracle:oci:@localhost:1522:orcl XDB welcome1 /public MyFile.txt text/plain 19.08.2014 11:50:26 oracle.jcr.impl.OracleRepositoryImpl login INFO: JCR repository descriptors: query.xpath.pos.index = true option.versioning.supported = false jcr.repository.version = 11.1.0.0.0 option.observation.supported = false option.locking.supported = false oracle.jcr.framework.version = 11.1.0.0.0 query.xpath.doc.order = false jcr.specification.version = 1.0 jcr.repository.vendor = Oracle option.query.sql.supported = false jcr.specification.name = Content Repository for Java Technology API level.2.supported = true level.1.supported = true jcr.repository.name = XML DB Content Connector jcr.repository.vendor.url = http://www.oracle.com oracle.jcr.persistenceManagerFactory = oracle.jcr.impl.xdb.XDBPersistenceManagerFactory option.transactions.supported = false 19.08.2014 11:50:26 oracle.jcr.impl.OracleRepositoryImpl login INFO: Session Session-1 connected for user id XDB 19.08.2014 11:50:27 oracle.jcr.impl.OracleSessionImpl logout INFO: Session-1: logout instead of C:\Oracle\Database\product\11.2.0\dbhome_1>java UploadFile jdbc:oracle:oci:@localhost:1522:orcl XDB welcome1 /public MyFile.txt text/plain 19.08.2014 10:56:39 oracle.jcr.impl.OracleRepositoryImpl login INFO: JCR repository descriptors: query.xpath.pos.index = true option.versioning.supported = false jcr.repository.version = 11.1.0.0.0 option.observation.supported = false option.locking.supported = false oracle.jcr.framework.version = 11.1.0.0.0 query.xpath.doc.order = false jcr.specification.version = 1.0 jcr.repository.vendor = Oracle option.query.sql.supported = false jcr.specification.name = Content Repository for Java Technology API level.2.supported = true level.1.supported = true jcr.repository.name = XML DB Content Connector jcr.repository.vendor.url = http://www.oracle.com oracle.jcr.persistenceManagerFactory = oracle.jcr.impl.xdb.XDBPersistenceManagerFactory option.transactions.supported = false 19.08.2014 10:56:39 oracle.jcr.impl.OracleRepositoryImpl login INFO: Session Session-1 connected for user id XDB Exception in thread "main" javax.jcr.RepositoryException: Unable to accept binary content at oracle.jcr.impl.ExceptionFactory.repository(ExceptionFactory.java:142) at oracle.jcr.impl.ExceptionFactory.otherwiseFailed(ExceptionFactory.java:98) at oracle.jcr.impl.xdb.XDBPersistenceManager.acceptBinaryStream(XDBPersistenceManager.java:1421) at oracle.jcr.impl.xdb.XDBResource.setContent(XDBResource.java:898) at oracle.jcr.impl.ContentNode.setProperty(ContentNode.java:472) at oracle.jcr.impl.OracleNode.setProperty(OracleNode.java:1439) at oracle.jcr.impl.OracleNode.setProperty(OracleNode.java:460) at UploadFile.main(UploadFile.java:54) Caused by: java.sql.SQLException: Invalid argument(s) in call at oracle.jdbc.driver.T2CConnection.newOutputStream(T2CConnection.java:2392) at oracle.sql.BLOB.setBinaryStream(BLOB.java:893) at oracle.jcr.impl.xdb.XDBPersistenceManager.acceptBinaryStream(XDBPersistenceManager.java:1393) ... 5 more

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• Reducing Deadlocks - not a DBA issue ?

  - by steveh99999

   As a DBA, I'm involved on an almost daily basis troubleshooting 'SQL Server' performance issues. Often, this troubleshooting soon veers away from a 'its a SQL Server issue' to instead become a wider application/database design/coding issue.One common perception with SQL Server is that deadlocking is an application design issue - and is fixed by recoding...  I see this reinforced by MCP-type questions/scenarios where the answer to prevent deadlocking is simply to change the order in code in which tables are accessed....Whilst this is correct, I do think this has led to a situation where many 'operational' or 'production support' DBAs, when faced with a deadlock, are happy to throw the issue over to developers without analysing the issue further....A couple of 'war stories' on deadlocks which I think are interesting :- Case One , I had an issue recently on a third-party application that I support on SQL 2008.  This particular third-party application has an unusual support agreement where the customer is allowed to change the index design on the third-party provided database.  However, we are not allowed to alter application code or modify table structure..This third-party application is also known to encounter occasional deadlocks – indeed, I have documentation from the vendor that up to 50 deadlocks per day is not unusual !So, as a DBA I have to support an application which in my opinion has too many deadlocks - but, I cannot influence the design of the tables or stored procedures for the application. This should be the classic - blame the third-party developers scenario, and hope this issue gets addressed in a future application release - ie we could wait years for this to be resolved and implemented in our production environment...But, as DBAs  can change the index layout, is there anything I could do still to reduce the deadlocks in the application ?I initially used SQL traceflag 1222 to write deadlock detection output to the SQL Errorlog – using this I was able to identify one table heavily involved in the deadlocks.When I examined the table definition, I was surprised to see it was a heap – ie no clustered index existed on the table.Using SQL profiler to see locking behaviour and plan for the query involved in the deadlock, I was able to confirm a table scan was being performed.By creating an appropriate clustered index - it was possible to produce a more efficient plan and locking behaviour.So, less locks, held for less time = less possibility of deadlocks. I'm still unhappy about the overall number of deadlocks on this system - but that's something to be discussed further with the vendor.Case Two,  a system which hadn't changed for months suddenly started seeing deadlocks on a regular basis. I love the 'nothing's changed' scenario, as it gives me the opportunity to appear wise and say 'nothings changed on this system, except the data'.. This particular deadlock occurred on a table which had been growing rapidly. By using DBCC SHOW_STATISTICS - the DBA team were able to see that the deadlocks seemed to be occurring shortly after auto-update stats had regenerated the table statistics using it's default sampling behaviour.As a quick fix, we were able to schedule a nightly UPDATE STATISTICS WITH FULLSCAN on the table involved in the deadlock - thus, greatly reducing the potential for stats to be updated via auto_update_stats, consequently reducing the potential for a bad plan to be generated based on an unrepresentative sample of the data. This reduced the possibility of a deadlock occurring.  Not a perfect solution by any means, but quick, easy to implement, and needed no application code changes. This fix gave us some 'breathing space'  to properly fix the code during the next scheduled application release.   The moral of this post - don't dismiss deadlocks as issues that can only be fixed by developers...

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• System.Threading.Timer keep reference to it.

  - by Daniel Bryars

  According to [http://msdn.microsoft.com/en-us/library/system.threading.timer.aspx][1] you need to keep a reference to a System.Threading.Timer to prevent it from being disposed. I've got a method like this: private void Delay(Action action, Int32 ms) { if (ms <= 0) { action(); } System.Threading.Timer timer = new System.Threading.Timer( (o) => action(), null, ms, System.Threading.Timeout.Infinite); } Which I don't think keeps a reference to the timer, I've not seen any problems so far, but that's probably because the delay periods used have been pretty small. Is the code above wrong? And if it is, how to I keep a reference to the Timer? I'm thinking something like this might work: class timerstate { internal volatile System.Threading.Timer Timer; }; private void Delay2(Action action, Int32 ms) { if (ms <= 0) { action(); } timerstate state = new timerstate(); lock (state) { state.Timer = new System.Threading.Timer( (o) => { lock (o) { action(); ((timerstate)o).Timer.Dispose(); } }, state, ms, System.Threading.Timeout.Infinite); } The locking business is so I can get the timer into the timerstate class before the delegate gets invoked. It all looks a little clunky to me. Perhaps I should regard the chance of the timer firing before it's finished constructing and assigned to the property in the timerstace instance as negligible and leave the locking out.

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• SQL deadlock on delete then bulk insert

  - by StarLite

  I have an issue with a deadlock in SQL Server that I haven't been able to resolve. Basically I have a large number of concurrent connections (from many machines) that are executing transactions where they first delete a range of entries and then re-insert entries within the same range with a bulk insert. Essentially, the transaction looks like this BEGIN TRANSACTION T1 DELETE FROM [TableName] WITH( XLOCK HOLDLOCK ) WHERE [Id]=@Id AND [SubId]=@SubId INSERT BULK [TableName] ( [Id] Int , [SubId] Int , [Text] VarChar(max) COLLATE SQL_Latin1_General_CP1_CI_AS ) WITH(CHECK_CONSTRAINTS, FIRE_TRIGGERS) COMMIT TRANSACTION T1 The bulk insert only inserts items matching the Id and SubId of the deletion in the same transaction. Furthermore, these Id and SubId entries should never overlap. When I have enough concurrent transaction of this form, I start to see a significant number of deadlocks between these statements. I added the locking hints XLOCK HOLDLOCK to attempt to deal with the issue, but they don't seem to be helpling. The canonical deadlock graph for this error shows: Connection 1: Holds RangeX-X on PK_TableName Holds IX Page lock on the table Requesting X Page lock on the table Connection 2: Holds IX Page lock on the table Requests RangeX-X lock on the table What do I need to do in order to ensure that these deadlocks don't occur. I have been doing some reading on the RangeX-X locks and I'm not sure I fully understand what is going on with these. Do I have any options short of locking the entire table here?

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• How do I lock the workstation from a windows service?

  - by Brad Mathews

  Hello, I need to lock the workstation from a windows service written in VB.Net. I am writing the app on Windows 7 but it needs to work under Vista and XP as well. User32 API LockWorkStation does not work as it requires an interactive desktop and I get return value of 0. I tried calling %windir%\System32\rundll32.exe user32.dll,LockWorkStation from both a Process and from Shell, but still nothing happens. Setting the service to interact with the desktop is a no-go as I am running the service under the admin account so it can do some other stuff that requires admin rights - like disabling the network, and you can only select the interact with desktop option if running under Local System Account. That would be secondary question - how to run another app with admin rights from a service running under Local System Account without bugging the user. I am writing an app to control my kids computer/internet access (which I plan to open source when done) so I need everything to happen as stealthily as possible. I have a UI that handles settings and status notifications in the taskbar, but that is easy to kill and thus defeat the locking. I could make another hidden Windows Forms app to handle the locking, but that just seems a rather inelegant solution. Better ideas anyone? Thanks! Brad

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• What version control system is best designed to *prevent* concurrent editing?

  - by Fred Hamilton

  We've been using CVS (with TortoiseCVS interface) for years for both source control and wide-ranging document control (including binaries such as Word, Excel, Framemaker, test data, simulation results, etc.). Unlike typical version control systems, 99% of the time we want to prevent concurrent editing - when a user starts editing a file, the pre-edit version of the file becomes read only to everyone else. Many of the people who will be using this are not programmers or even that computer savvy, so we're also looking for a system that let's people simply add documents to the repository, check out and edit a document (unless someone else is currently editing it), and check it back in with a minimum of fuss. We've gotten this to work reasonably well with CVS + TortoiseCVS, but we're now considering Subversion and Mercurial (and open to others if they're a better fit) for their better version tracking, so I was wondering which one supported locking files most transparently. For example, we'd like exclusive locking enabled as the default, and we want to make it as difficult as possible for someone to accidentally start editing a file that someone else has checked out. For example when someone checks out a file for editing, it checks with the master database first even if they have not recently updated their sandbox. Maybe it even won't let a user check out a document if it's off the network and can't check in with the mothership.

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• Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

  - by lazyconfabulator

  I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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• In .NET when Aborting Thread, can this piece of code get corrupted?

  - by bosko

  Little intro: In complex multithreaded aplication (enterprise service bus EBS), I need to use Thread.Abort, because this EBS accepts user written modules which communicates with hardware security modules. So if this module gets deadlocked or hardware stops responding - i need to just unload this module and rest of this server aplication must keep runnnig. So there is abort sync mechanism which ensures that code can be aborted only in user section and this section must be marked as AbortAble. If this happen there is possibility that ThreadAbortException will be thrown in this pieace of code: public void StopAbortSection() { var id = Thread.CurrentThread.ManagedThreadId; lock (threadIdMap[id]) { .... } } If module is on AbortSection and Aplication decides to abort module, but after this decision but before actual Thread.Abort, module enters NonAbortableSection by calling this method, but lock is actualy taken on that locking object. So lock will block until Abort or abort can be executed before reaching this block by this code. But Object with this method is essential and i need to be sure that this pieace of code is safe to abort in any moment. Probably i have to mention that threadIdMap is Dictionary(int,ManualResetEvent), so locking object is instance of ManualResetEvent. I hope you now understad my question. Sorry for its largeness.

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• Mutex example / tutorial ?

  - by Nav

  I've noticed that asking questions for the sake of creating a reference list etc. is encouraged in SO. This is one such question, so that anyone Googling for a mutex tutorial will find a good one here. I'm new to multithreading, and was trying to understand how mutexes work. Did a lot of Googling and this is the only decent tutorial I found, but it still left some doubts of how it works because I created my own program and the locking didn't work. One absolutely non-intuitive syntax of the mutex is pthread_mutex_lock( &mutex1 );, where it looks like the mutex is being locked, when what I really want to lock is some other variable. Does this syntax mean that locking a mutex locks a region of code until the mutex is unlocked? Then how do threads know that the region is locked? And isn't such a phenomenon supposed to be called critical section? In short, could you please help with the simplest possible mutex example program and the simplest possible explanation on the logic of how it works? I'm sure this will help plenty of other newbies.

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• Using ember-resource with couchdb - how can i save my documents?

  - by Thomas Herrmann

  I am implementing an application using ember.js and couchdb. I choose ember-resource as database access layer because it nicely supports nested JSON documents. Since couchdb uses the attribute _rev for optimistic locking in every document, this attribute has to be updated in my application after saving the data to the couchdb. My idea to implement this is to reload the data right after saving to the database and get the new _rev back with the rest of the document. Here is my code for this: // Since we use CouchDB, we have to make sure that we invalidate and re-fetch // every document right after saving it. CouchDB uses an optimistic locking // scheme based on the attribute "_rev" in the documents, so we reload it in // order to have the correct _rev value. didSave: function() { this._super.apply(this, arguments); this.forceReload(); }, // reload resource after save is done, expire to make reload really do something forceReload: function() { this.expire(); // Everything OK up to this location Ember.run.next(this, function() { this.fetch() // Sub-Document is reset here, and *not* refetched! .fail(function(error) { App.displayError(error); }) .done(function() { App.log("App.Resource.forceReload fetch done, got revision " + self.get('_rev')); }); }); } This works for most cases, but if i have a nested model, the sub-model is replaced with the old version of the data just before the fetch is executed! Interestingly enough, the correct (updated) data is stored in the database and the wrong (old) data is in the memory model after the fetch, although the _rev attribut is correct (as well as all attributes of the main object). Here is a part of my object definition: App.TaskDefinition = App.Resource.define({ url: App.dbPrefix + 'courseware', schema: { id: String, _rev: String, type: String, name: String, comment: String, task: { type: 'App.Task', nested: true } } }); App.Task = App.Resource.define({ schema: { id: String, title: String, description: String, startImmediate: Boolean, holdOnComment: Boolean, ..... // other attributes and sub-objects } }); Any ideas where the problem might be? Thank's a lot for any suggestion! Kind regards, Thomas

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• Fastest inline-assembly spinlock

  - by sigvardsen

  I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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• Testing approach for multi-threaded software

  - by Shane MacLaughlin

  I have a piece of mature geospatial software that has recently had areas rewritten to take better advantage of the multiple processors available in modern PCs. Specifically, display, GUI, spatial searching, and main processing have all been hived off to seperate threads. The software has a pretty sizeable GUI automation suite for functional regression, and another smaller one for performance regression. While all automated tests are passing, I'm not convinced that they provide nearly enough coverage in terms of finding bugs relating race conditions, deadlocks, and other nasties associated with multi-threading. What techniques would you use to see if such bugs exist? What techniques would you advocate for rooting them out, assuming there are some in there to root out? What I'm doing so far is running the GUI functional automation on the app running under a debugger, such that I can break out of deadlocks and catch crashes, and plan to make a bounds checker build and repeat the tests against that version. I've also carried out a static analysis of the source via PC-Lint with the hope of locating potential dead locks, but not had any worthwhile results. The application is C++, MFC, mulitple document/view, with a number of threads per doc. The locking mechanism I'm using is based on an object that includes a pointer to a CMutex, which is locked in the ctor and freed in the dtor. I use local variables of this object to lock various bits of code as required, and my mutex has a time out that fires my a warning if the timeout is reached. I avoid locking where possible, using resource copies where possible instead. What other tests would you carry out?

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• What do I do about a Java program that spawned two instaces of itself?

  - by user288915

  I have a java JAR file that is triggered by a SQL server job. It's been running successfully for months. The process pulls in a structured flat file to a staging database then pushes that data into an XML file. However yesterday the process was triggered twice at the same time. I can tell from a log file that gets created, it looks like the process ran twice simultaneously. This caused a lot of issues and the XML file that it kicked out was malformed and contained duplicate nodes etc. My question is, is this a known issue with Java JVM's spawning multiple instances of itself? Or should I be looking at sql server as the culprit? I'm looking into 'socket locking' or file locking to prevent multiple instances in the future. This is the first instance of this issue that I've ever heard of. More info: The job is scheduled to run every minute. The job triggers a .bat file that contains the java.exe - jar filename.jar The java program runs, scans a directory for a file and then executes a loop to process if the file if it finds one. After it processes the file it runs another loop that kicks out XML messages. I can provide code samples if that would help. Thank you, Kevin

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• What are jQuery best practices regarding Ajax convenience methods and error handling?

  - by JonathanHayward

  Let's suppose, for an example, that I want to partly clone Gmail's interface with jQuery Ajax and implement periodic auto-saving as well as sending. And in particular, let us suppose that I care about error handling, expecting network and other errors, and instead of just being optimistic I want sensible handling of different errors. If I use the "low-level" feature of $.ajax() then it's clear how to specify an error callback, but the convenience methods of $.get(), $.post(), and .load() do not allow an error callback to be specified. What are the best practices for pessimistic error handling? Is it by registering a .ajaxError() with certain wrapped sets, or an introspection-style global error handler in $.ajaxSetup()? What would the relevant portions of code look like to initiate an autosave so that a "could not autosave" type warning is displayed if an attempted autosave fails, and perhaps a message that is customized to the type of error? Thanks,

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• How to figure the read/write ratio in Sql Server?

  - by Bill Paetzke

  How can I query the read/write ratio in Sql Server 2005? Are there any caveats I should be aware of? Perhaps it can be found in a DMV query, a standard report, a custom report (i.e the Performance Dashboard), or examining a Sql Profiler trace. I'm not sure exactly. Why do I care? I'm taking time to improve the performance of my web app's data layer. It deals with millions of records and thousands of users. One of the points I'm examining is database concurrency. Sql Server uses pessimistic concurrency by default--good for a write-heavy app. If my app is read-heavy, I might switch it to optimistic concurrency (isolation level: read uncommitted snapshot) like Jeff Atwood did with StackOverflow.

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• How to avoid StaleObjectStateException when transaction updates thousands of entities?

  - by ThinkFloyd

  We are using Hibernate 3.6.0.Final with JPA 2 and Spring 3.0.5 for a large scale enterprise application running on tomcat 7 and MySQL 5.5. Most of the transactions in application, lives for less than a second and update 5-10 entities but in some use cases we need to update more than 10-20K entities in single transaction, which takes few minutes and hence more than 70% of times such transaction fails with StaleObjectStateException because some of those entities got updated by some other transaction. We generally maintain version column in all tables and in case of StaleObjectStateException we generally retry but since these longs transactions are anyways very long so if we keep on retrying then also I am not very sure that we'll be able to escape StaleObjectStateException. Also lot of activities keep updating these entities in busy hours so we cannot go with pessimistic approach because it can potentially halt many activities in system. Please suggest how to fix such long transaction issue because we cannot spawn thousands of independent and small transactions because we cannot afford messed up data in case of some failed & some successful transactions.

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• Mysql Slave stuck in "System lock"

  - by Greg

  My MySQL slave is spending a lot of time in Slave_SQL_Running_State: System lock. I can see that the system is currently I/O write bound, and that it is processing the log, although slowly. Show processlist doesn't show anything other than "Waiting for master to send event" and "System lock" when it is in this state. All my tables (other than the system tables) are InnoDB, and external locking is disabled. What is the slave doing in this state?

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• Installing WindowsAuthentication breaks authentication / web.config?

  - by Ian Quigley

  I have a clean Windows 2008 R2 box (on a VM) and have installed IIS 7.5 with default options. I then copied a website to it (from Windows 7, IIS 7) and after a little tweaking the website is working fine. The website is currently using and working with Anonymous Authentication. I have gone back to the Windows Components/Sever Manager, Roles - Security and ticked and installed Windows Authentication. When I check my server in IIS (top level above sites) - Authentication, I see Anonymous Authentication (enabled) ASP.NET Impersonation (disabled) Forms Authentication (disbaled) Windows Authentication (enabled) When I check my default website - Authentication, I see as above but "Retrieving status" and an error dialog saying There was an error while performing this operation. Details: Filename c:\inetpub\wwwroot\screwturnwiki\web.config Line number: 96 Error: This configuration section cannot be used in this path. This happens when the section is being locked at the parent level. Locking is either by default (overriderModeDefault="Deny"), or set explicity by a location tag with overrideMode="Deny" or the legacy allowOverride="False". I have tried hand editing the web.config with no success. (How to use locking in IIS7 Configuration) UN-installing Windows Authentication happily returns my site to working with Anonymous Authentication, and allows me to enable/disable these three options. FYI. I am using ScrewTurnWiki with the Active Directory plug in. It all works fine under Windows 7 IIS 7 locally (has been for months) Web.Config <system.webServer> (edit) <handlers> ( deleted removes/adds ) </handlers> <security> <authentication> 96: <windowsAuthentication enabled="true" useKernelMode="true"> <extendedProtection tokenChecking="Allow" /> <providers> <clear /> <add value="NTLM" /> <add value="Negotiate" /> </providers> </windowsAuthentication> </authentication> </security>

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• Outlook 2007 freezes my system when I start it says it is "synchonizing folders"

  - by buzz

  When I try to start Outlook 2007, my system freezes, and Outlook says it is "synchonizing folders". I don't use exchange, and haven't seen any answers online. I've tried turning off the exchange integration (right clicking my folders) Since doing the latter, there is no longer an icon in the system tray when this is frozen (there was before) UPDATE: It seems my anti-virus program (comodo) was what was actually locking during Outlook file synch. I disabled that, and things seemed to settle down.

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• Xforwarding in Ubuntu

  - by Dan

  I'm trying to get Xforwarding working in Ubuntu... On the server I have uncommented the following lines of /etc/ssh/sshd_config: X11Forwarding yes AllowTcpForwarding yes Now I try to ssh in, but I get the following error messages (and Xforwarding isn't working). $ssh -Y example.com /usr/bin/xauth: /home/dan/.Xauthority not writable, changes will be ignored $ssh -X example.com /usr/bin/xauth: error in locking authority file /home/dan/.Xauthority Any suggestions? Thanks

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• copy windows registry and/or other locked files

  - by karolrvn

  Hi. While improving my (personal) backup system, I noticed, that I cannot copy certain locked files, like the windows registry files. Is there a way to copy such things? Or a specific solution for the registry (I know of the regedit-File-Export ,,solution'' but this is to text format and seems slow). AFAIK, On Linux the locking system is advisory and on Windows it is mandatory. Can I somehow bypass the mandatory-ness for backup purposes etc.? TIA.

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• Decoding PAM configuration files ...

  - by Jamie

  Could someone point me to some (recent) documentation that would help me with decoding PAM configuration file lines like this: auth [success=2 default=ignore] pam_unix.so nullok_secure auth [success=1 default=ignore] pam_winbind.so krb5_auth krb5_ccache_type=FILE cached_login try_first_pass I'm trying to get my Ubuntu box (testing 10.04 Server Beta 2) to use Active Directory, and the last step is to get PAM on the unix box to work, but I'm wary about making changes (and locking myself out) without understanding how to merge what I'm reading here with what ubuntu has implemented.

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• APC (PHP Cache) Uptime 0 minutes, not caching

  - by Jussi

  My goal is to implement APC for opcode cache for a drupal 6 production site. I have so far tested APC with several php files with and without including other php files with include_once. Also tried to tweak the apc.ini values for shm_size, apc.include_once_override and apc.stat. Restarted apache every time. Resulting in apc.php not showing any changes in any values. (except of course the changed apc.ini values are shown as they should) Every time i refresh the apc.php test page, the start time resets as the current time showing uptime 0 minutes. apc.php -testpage shows: General Cache InformationAPC Version 3.1.9 PHP Version 5.2.10 APC Host xxxx.xx.xx Server Software Apache/2.2.3 (CentOS) Shared Memory 1 Segment(s) with 128.0 MBytes (mmap memory, pthread mutex Locks locking) Start Time 2011/07/26 11:53:56 Uptime 0 minutes File Upload Support 1 Cached Files 0 ( 0.0 Bytes) Hits 1 Misses 1 Request Rate (hits, misses) 2.00 cache requests/second Hit Rate 1.00 cache requests/second Miss Rate 1.00 cache requests/second Insert Rate 0.00 cache requests/second Cache full count 0 Cached Variables 0 ( 0.0 Bytes) Hits 0 Misses 0 Request Rate (hits, misses) 0.00 cache requests/second Hit Rate 0.00 cache requests/second Miss Rate 0.00 cache requests/second Insert Rate 0.00 cache requests/second Cache full count 0 apc.cache_by_default 1 apc.canonicalize 1 apc.coredump_unmap 0 apc.enable_cli 0 apc.enabled 1 apc.file_md5 0 apc.file_update_protection 2 apc.filters apc.gc_ttl 3600 apc.include_once_override 0 apc.lazy_classes 0 apc.lazy_functions 0 apc.max_file_size 16 apc.mmap_file_mask /tmp/apcphp5.095eRm apc.num_files_hint 1024 apc.preload_path apc.report_autofilter 0 apc.rfc1867 0 apc.rfc1867_freq 0 apc.rfc1867_name APC_UPLOAD_PROGRESS apc.rfc1867_prefix upload_ apc.rfc1867_ttl 3600 apc.serializer default apc.shm_segments 1 apc.shm_size 128M apc.slam_defense 0 apc.stat 0 apc.stat_ctime 0 apc.ttl 7200 apc.use_request_time 1 apc.user_entries_hint 4096 apc.user_ttl 7200 apc.write_lock 1 Host Status Diagrams: Free: 128.0 MBytes (100.0%) Hits: 1 (50.0%) Used: 20.3 KBytes (0.0%) Misses: 1 (50.0%) Detailed Memory Usage and Fragmentation: Fragmentation: 0% phpinfo shows: Server API CGI/FastCGI APC: Version 3.1.9 APC Debugging Enabled MMAP Support Enabled MMAP File Mask /tmp/apcphp5.JkKDk7 Locking type pthread mutex Locks Serialization Support php Revision $Revision: 308812 $ Build Date Jul 21 2011 14:31:12 I followed these steps to find if suexec settings would prevent caching: http://www.litespeedtech.com/support/forum/showthread.php?t=4189 [root@host /]# ps -ef|grep lsphp root 20402 17833 0 11:21 pts/0 00:00:00 grep lsphp [root@host /]# ps -waux root 17833 0.0 0.1 5004 1484 pts/0 S 10:39 0:00 bash ..indicates that there is no lsphp running on the host also I read the following article and comments, concluding that in my case the problem is not the suexec as the user apache is the httpd process owner http://www.brandonturner.net/blog/2009/07/fastcgi_with_php_opcode_cache/ also suexec command is not recognized when logged and launced as root @ host also i'm almost confident that there is no cPanel running on the host to check if a setting there would reset the running cache process at some interval This leaves me with few clues where to head next. I tried to set (with chown and chgrp) apache as the owner of the apc.php file and some test php files resulting in 500 server error. Is there a way to check if the file permissions prevent the apc stay running? I'm tremendously grateful for any suggestions or help.

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• When and why would Windows Explorer lock an external hard disk?

  - by Ngu Soon Hui

  I am quite surprised to see that Windows Explorer is locking my external hard disk. Is there any reason why explorer.exe is holding on to my external hard disk? Before I was trying to detach the external hard disk, I was opening a csproj file using Visual Studio 2008. I made sure that I closed down Visual Studio before trying to detach the external hard disk. There was no other active program except Google Chrome, from what I could see, that was running.

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