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Description:
This wait type is when a thread is waiting for access to the AG work queue so that it can wait for some work.
(Books Online description: “Concurrency control wait on the AlwaysOn Availability Groups background work task object.”)
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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 764 in 2012 and 782 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.
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for access to the AG work queue
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PostWait+90
EventInternal<SuspendQueueSLock>::Wait+2c6
SOS_RWLock::GetLongWait+10b
HadrWorkRoutine+5a8
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+a8