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Description:
This wait type is when a thread switches to preemptive mode as part of querying the state of a session target.
(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 541 in 2008 and 2008 R2, 589 in 2012, and 605 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.
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):
- Getting the target state (in this case, as part of a query involving the sys.fn_xe_file_target_read_file function)
And other similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PopWait+0xb4
XE_Engine::GetTargetState+0xc4
CSessionTargetsTable::GetTargetStatus+0x58
CSessionTargetsTable::InternalGetRow+0x151
CQScanTVFStreamNew::GetRow+0xd6
CQScanFilterNew::GetRowHelper+0xc4
CQScanNLJoinTrivialNew::GetRow+0xeb
CQueryScan::GetRow+0x81
CXStmtQuery::ErsqExecuteQuery+0x4df
CXStmtSelect::XretExecute+0x322
CMsqlExecContext::ExecuteStmts<1,1>+0x40d
CMsqlExecContext::FExecute+0xa9e
CSQLSource::Execute+0x981
process_request+0xe61
process_commands_internal+0x2df
process_messages+0x253
SOS_Task::Param::Execute+0x231
SOS_Scheduler::RunTask+0xaa