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Description:
This wait type is when a thread is calling the Windows SetFileValidData function as part of creating or growing a data file under Instant File Initialization.
(Books Online description: N/A)
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Added in SQL Server version:
2008
Removed in SQL Server version:
N/A
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 464 in 2008 and 2008 R2, 512 in 2012, and 528 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.
Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as RUNNING, as SQL Server doesn’t know what Windows is doing with the thread.
Known occurrences in SQL Server (list number matches call stack list):
- Setting the valid end of the file (in this case, while creating a new database)
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PopWait+0xb1
AutoSwitchPreemptive::~AutoSwitchPreemptive+0x95
FCB::InitializeSpace+0x1d3
FileMgr::CreateNewFile+0x10e
AsynchronousDiskAction::ExecuteDeferredAction+0x8f
AsynchronousDiskWorker::ThreadRoutine+0x15c
SubprocEntrypoint+0xa7f
SOS_Task::Param::Execute+0x21e
SOS_Scheduler::RunTask+0xab