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PREEMPTIVE_FSRECOVER_UNCONDITIONALUNDO

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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.

Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.

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):

  1. 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):

  1. 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