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Description:
This wait type is when SQL Server is starting and initializes the background checkpoint process.
(Books Online description: “Occurs at server startup to tell the checkpoint thread that it can start.”)
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Added in SQL Server version:
Pre-2005/2005
Removed in SQL Server version:
N/A
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 101 in all versions through 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. There should only be one of these waits be instance startup, unless the background checkpoint process crashed and restarted (which I’ve never seen happen).
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):
- Starting the background checkpoint process
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PostWait+9e
EventInternal<SuspendQueueSLock>::Wait+1fb
CheckpointThread+49
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+ab