Preemptive waits means that something is interrupting SQL Server and the database is waiting for this to complete. Non-Preemptive means that there is cooperation with SQL Server.

In this case the PREEMPTIVE_OS_COMOPS wait means that SQL Server has been preempted (not cooperating) by the operating system and is currently waiting for the OS to complete its task. This is likely not caused by a specific query, rather the query is showing the symptoms of the problem.

The PREEMPTIVE_OS_COMOPS wait type was introduced in SQL Server 2008.


If you are seeing this wait type it may be an indicator that are running on your server that are taking up resources that are needed by SQL Server. It might also be an indicator that a VM backup is occurring, or other VM configuration may be impacting your SQL Server performance.

Database Health Monitor historic wait monitoring system can help you track down when these waits are occurring and what queries are causing or are impacted by the PREEMPTIVE_OS_COMOPS wait type. The Database Health Monitor is a free tool for Microsoft SQL Server 2005, 2008, 2008R2, 2012, 2014, and newer create by Steve Stedman.

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