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Description:
This wait type is where a thread has switched to preemptive mode to perform rollback of a FILESTREAM operation on the file system.
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Added in SQL Server version:
2008
Removed in SQL Server version:
N/A
Extended Events wait_type value:
Maps to the PREEMPTIVE_FSRECOVER_CONDITIONALUNDO map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here).
The map_key value in sys.dm_xe_map_values is 516 in 2008 and 2008 R2, 564 in 2012, and 580 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 to be a noticeable contention point.
Known occurrences in SQL Server (list number matches call stack list):
- Rolling back a FILESTREAM operation (in this case, as part of rolling back the insertion of a row that contains FILESTREAM data)
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PopWait+0xb1
AutoSwitchPreemptive::~AutoSwitchPreemptive+0x95
FsRecoveryOperation::ConditionalUndo+0x11c
FsRecoveryOperation::Undo+0xfd
FsRecoveryManager::UndoFromRollback+0x164
XdesRMReadWrite::RollbackToLsn+0xcde
XdesRMFull::RollbackNested+0x29b
XactRM::RollbackNestedXact+0xff
FullXactImpBase::RollbackNestedXact+0x53
CMsqlXactInternalReadWrite::RollbackNestedXact+0x5d
CMsqlXactImp::RollbackNestedXact+0x19
CAutoMsqlXact::RollbackNestedXact+0x5b
CXStmtDML::RollbackNestedXact+0x1b
CXStmtDML::FinishOnExceptionImp+0x1a7
CMsqlExecContext::FExecute+0xa58
CSQLSource::Execute+0x86c
CStmtPrepQuery::XretPrepQueryExecute+0x464
CMsqlExecContext::ExecuteStmts<1,1>+0x427