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I am guessing this wait type is when a worker (think ‘thread’) is being moved to a scheduler, and the wait type was added to allow tracking worker migrations between schedulers in a NUMA node, which can now occur in 2019 when a thread is at the head of the runnable queue in a scheduler.

(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 174  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 be a noticeable contention point.

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

  1. Waiting for a thread to be placed on a scheduler.

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

  1. sqldk.dll!SOS_Task::PostWait+0x6f