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Description:
This wait type is when a thread is calling the Windows WinVerifyTrust function.
(Books Online description: “Internal use only.”)
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Added in SQL Server version:
2016
Removed in SQL Server version:
N/A
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 1055 in 2016 RTM. After 2016 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):
- Verifying trust, in this case while loading a DLL.
And other similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PopWait+0x107
SOS_ExternalAutoWait::~SOS_ExternalAutoWait+0x5f
SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+0x5c
CSECUtilities::DBLoadLibraryW+0x516
LoadXPDllHelper+0xe3
FCallRpcDLL+0x1a9
CXProc::Execute+0x6c9
CSQLSource::Execute+0xdac
CStmtExecProc::XretLocalExec+0x2c0
CStmtExecProc::XretExecExecute+0x5d7
CXStmtExecProc::XretExecute+0x38
CMsqlExecContext::ExecuteStmts<1,1>+0x8f8
CMsqlExecContext::FExecute+0x946
CSQLSource::Execute+0xb9f