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Description:
This wait type is a generic wait for when a thread is calling one of several Windows functions related to DLLs.
(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 467 in 2008 and 2008 R2, 515 in 2012, and 531 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):
- Performing an operation with a DLL (in this case, while initializing the full text subsystem)
- Performing an operation with a DLL (in this case, while preparing an XML document)
And other similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):
- XeSosPkg::wait_info_external::Publish+138
SOS_Scheduler::UpdateWaitTimeStats+543
SOS_Task::PopWait+b1
SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
CFTCrawlManager::FInit+820
InitFulltextCrawlManager+9
StartUp::OpenDBsAndRecover+7fc
StartUp::InitDBMS+aa
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+ab - SOS_Task::PopWait+ba
AutoSwitchPreemptive::~AutoSwitchPreemptive+6e
CXMLDocsList::LoadDocument+1d5
CXMLDocParamInfo::Load+a0
SpXmlPrepareDocument+20e
CSpecProc::ExecuteSpecial+112
CXProc::Execute+e3
CSQLSource::Execute+9c0