PREEMPTIVE_OS_DELETEFILE

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Description:

This wait type is when a thread is calling the Windows DeleteFile function.

(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 447 in 2008 and 2008 R2, 495 in 2012, and 511 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):

1. Deleting a file (in this case, while removing old trace files while initializing C2-compliant tracing during instance startup)
2. Deleting a file (in this case, as part of a DROP DATABASE operation)
3. Deleting a file (in this case, while removing the backup checkpoint file from when the previous backup operation was interrupted)

And other similar stacks.

Abbreviated call stacks (list number matches known occurrences list):

1. SOS_Task::PopWait+b1
   SOS_ExternalAutoWait::~SOS_ExternalAutoWait+7c
   CTrcFile::FDeleteOldTraceFile+1de
   CTrace::DeleteOldTraceFile+25
   CTraceFileIoProvider::OpenNextFile+2da
   CTraceFileIoProvider::Init+1a3
   CTraceFileIoProvider::CreateTraceIoProvider+91
   CTrace::Init+180
   CTraceController::CreateTrace+5f0
   CTraceController::SetupDefaultTrace+4ca
   InitializeC2Tracing+12b
   NotifyMasterDatabaseReady+4f
   StartUp::OpenDBsAndRecover+699
   StartUp::InitDBMS+aa
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab
2. SOS_Task::PopWait+b1
   AutoSwitchPreemptive::~AutoSwitchPreemptive+95
   DBDeleteFileW+c0
   AsynchronousDiskAction::DoDeleteFile+87
   AsynchronousDiskAction::ExecuteDeferredAction+e2
   AsynchronousDiskPool::PerformActionsSerially+61
   AsynchronousDiskPool::WaitUntilDoneOrTimeout+71
   AsynchronousDiskPool::WaitUntilDone+c
   AsynchronousDiskPool::WaitUntilDoneNoThrow+40
   NotifyEndDropDatabase::HandleEvent+12b
   XactRM::FireNotificationsInternal+cf
   XactRM::SinglePhaseCommit+4e1
   XactRM::CommitInternal+472
   FullXactImp::Commit+33f
   CMsqlXactInternalReadWrite::Commit+19
   CMsqlXactImp::Commit+1d6
   CAutoMsqlXact::CommitNestedXact+bf
   CStmtDropDB::XretExecute+d97
   CMsqlExecContext::ExecuteStmts<0,1>+8bd
   CMsqlExecContext::FExecute+a58
   CSQLSource::Execute+86c
   process_request+a57
3. SOS_Task::PopWait+b1
   AutoSwitchPreemptive::~AutoSwitchPreemptive+95
   DBDeleteFileW+c0
   BackupDeleteFile+14
   CheckpointableOperation::DeleteCheckpointFile+62
   BackupOperation::DeleteRestoreCheckpointFileWhenRestoreStarts+b0
   BackupOperation::Restore+431
   BackupEntry::RestoreLog+177
   CStmtLoadXact::XretExecute+105
   CMsqlExecContext::ExecuteStmts<1,1>+427
   CMsqlExecContext::FExecute+a43
   CSQLSource::Execute+86c
   process_request+a57
   process_commands+4a3
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab