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HADR_WORK_QUEUE

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Description:

This wait type is when a thread is waiting for some work to be entered into the AG work queue.

(Books Online description: “AlwaysOn Availability Groups background worker thread waiting for new work to be assigned. This is an expected wait when there are ready workers waiting for new work, which is the normal state.”)

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Added in SQL Server version:

2012

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 765 in 2012 and 783 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

I have not seen this wait type be a noticeable contention point.

This wait type is one that I usually filter out as a benign wait when doing wait statistics analysis.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for some AG work to do

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+1f9
    HadrThreadPool::DequeueWork+136
    HadrWorkRoutine+10b
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8