11/23/2023 0 Comments Ef set command timeout 0It will hold all the locks indefinitely (ok, not indefinitely, but for a very long time, until it is killed or somebody reuses exactly that same session). That means, it wont be rolled back, it wont be committed. When command timeout occurs (based on the CommandTimeout value), if XACT_ABORT is OFF, the explicit transaction that was running will leak. ![]() That is, until we kill that session, close that query editor window, or execute some other command in exactly that same session (that is why we opened the other window). Also, the session 57 is in “sleeping” status “forever” with an opened transaction. That means, transaction has begun, row1 is inserted, but row2 is NOT, and transaction is never committed – locks are here to stay. Let’s check sessions with sp_WhoIsActive and the locks with sys.dm_tran_locks in a SEPARATE query editor window (will be explained later why): But because CommandTimeout was set to 5 seconds, during that 8 second wait the timeout occured. The procedure was designed to begin a transaction, insert the row1, wait 8 seconds, insert the row2 and commit. The timeout period elapsed prior to completion of the operation or the server is not responding. ![]() CommandTimeoutBehavior on a SqlCommand with those three choices? That would remove the burden from the developers and save lots and lots of hours of many DBAs.Įnough talk, let’s reproduce it and see how it looks like! If you run this script: Would it be nice that Microsoft had a property e.g. leave it opened forever holding all the locks (that is the default “choice” of most of us!).And we all handle those pending transactions with explicit commit/rollback in our dotnet app, don’t we? We have three choices to do with pending transaction when timeout exception is raised in dotnet code: It is “by desgin” to let developers decide what will they do with pending transactions. That “leaking transaction” behavior is the same on all SqlClient versions I tried (dotnet 2.0, 4.0, 4.5.2) and all SQL Server versions I tried (SQL 2008, 2008R2, 2014). Transaction is still there, leaked, holding all the locks on a forever “sleeping” session! (sleeping beauty, only this one is rather “ugly”). All that “proper closing” of the connection will not abort the transaction and not even end the sleeping session (because of connection pooling, until that same connection is reused). You can do a “proper” try-catch Dispose of command, nicely Close/Dispose the connection or do it with a “using” construct. ![]() The session will stay forever in “sleeping” status. If client app does not explicitly commit or rollback, the transaction remains open, holding all the locks, blocking other sessions until somebody kills that session! Sounds familiar? Do you have occasional strange blocking with the root blocker that is sleeping session? If the client does not submit the rollback and continues other processing the transaction remains open and the behavior scope of the application becomes undefined.ĬommandTimeout will only STOP TSQL execution, but the client application is responsible to COMMIT or ROLLBACK the pending transaction (if not already rolled back because of SET XACT_ABORT ON). Timeout can be seen as a sql trace event of a class “Attention”:īob Dorr, Microsoft’s Senior Escalation Engineer has blogged about Attention event, so let me quote him:Īt the time of the attention the transaction is not rolled back unless transaction abort (XACT_ABORT) has been enabled. Your COMMIT command is also NOT executed if timeout occurred before it is reached (and often is). It is untrappable which means execution is NOT transferred to the “BEGIN CATCH” TSQL block. ![]() When timeout occurs, execution of the TSQL stops immediately. 0 means wait indefinitely, no timeout will be raised. If we ommit setting CommandTimeout property, the default of 30 seconds will be used. But, do we handle it properly? And what exactly is happening when the command timeout occurs? SqlCommand class has CommandTimeout property (do not mix it with the ConnectionTimeout which stops long login process). ADO.Net Data Provider for SQL Server ( namespace in assembly) has two common classes we often use: SqlConnection and SqlCommand.
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