If you are still running SQL Server 2000, then you are stuck with a single, somewhat limited, Trace Flag ( 1204). The means by which you can capture a deadlock graph have diversified and improved over recent versions of SQL Server. The first step in troubleshooting and resolving a deadlocking problem is to capture the deadlock graph information.Ī deadlock graph is an output of information regarding the sessions and resources that were involved in a deadlock. When 1205 errors are reported, it is important that the DBA finds out why the deadlock happened and takes steps to prevent its recurrence. Rollback cost – if two or more sessions involved in a deadlock have the same deadlock priority, then SQL Server will choose as the deadlock victim the session that has lowest estimated cost to roll back.Deadlock priority is covered in more detail later in this article. The session with the lowest priority will always be chosen as the deadlock victim. Deadlock priority – the assigned DEADLOCK_PRIORITY of a given session determines the relative importance of it completing its transactions, if that session is involved in a deadlock.SQL Server selects the deadlock victim based on the following criteria: Once the rollback completes, the victim’s session is terminated, returning a 1205 error message to the originating client. When this occurs, all of the locks held by the victim’s session are released, allowing any previously blocked other sessions to continue processing. When the Lock Monitor performs a deadlock search and detects that one or more sessions are embraced in a deadlock, one of the sessions is selected as a deadlock victim and its current transaction is rolled back.
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