![]() His three-part series uses the output from trace flag 1222 to demonstrate how to read the XML deadlock graph information, starting with Deadlock Troubleshooting, Part 1. The definitive source for understanding the output from trace flag 1222 is a series of blog posts written by Bart Duncan. ![]() Since the introduction of Extended Events and the new system_health event session in SQL Server 2008, deadlock information has been captured by default in SQL Server and no longer requires enabling additional data collection for analysis. SQL Trace, Event Notifications and WMI Alerts allow collection of the deadlock information as XML. Trace Flags 1222, 1205, or 1204 write the deadlock information as text into the ERRORLOG. Prior to SQL Server 2008, collecting deadlock information from SQL Server required enabling a trace flag, configuring a SQL Trace, Event Notifications, or using a WMI Alert. In a third-party vendor application, it may not be possible to make the changes necessary to eliminate deadlocks, but you can still collect information about the deadlocks to assist the third-party vendor in analysis and possibly identifying a solution to the problem. In SQL Server, the Lock Monitor background task is responsible for detecting and resolving deadlocks whenever they occur (basically terminating the session that has performed the least amount of work so far), and the resulting 1205 error can be a sign of problems that require further evaluation. Enjoy!ĭeadlocks occur in SQL Server whenever two processes attempt to acquire locks on the same resources in reverse order creating a persistently blocked condition, where neither of the sessions can continue to execute until the other session releases its locks. You can find all the other posts in this series at. ![]() It’s a little taster to let you know what we cover in our Immersion Event for The Accidental/Junior DBA, which we present several times each year. This month the SQLskills team is presenting a series of blog posts aimed at helping Accidental/Junior DBAs ‘keep the SQL Server lights on’.
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