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This wait type is for a background task that is sleeping between preallocating space in the Persistent Version Store for a database that has Accelerated Database Recovery enabled. When there is no activity taking place, this wait occurs every five minutes with a five minute duration. When there is a lot of activity, this wait occurs a lot more frequently with much smaller duration. This implies to me that the background PVS allocation task throttles up and down as needed.

(Books Online description: N/A)

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Added in SQL Server version:


Removed in SQL Server version:


Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 1378
in 2019 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 the background task timer to go off

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

  1. SOS_Task::PostWait+0x6f