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DUMP_LOG_COORDINATOR_QUEUE

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Description:

This wait type is when a thread is waiting for something to be produced by a log scanner during execution of the fn_dblog function, or by a backup log scanner during execution of the fn_dump_dblog 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 131 in 2008 and 2008 R2, and 135 in 2012 and 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.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for more log to process (in this case, while running fn_dblog)
  2. Waiting for more log to process (in this case, while running fn_dump_dblog – note the SubprocEntrypoint in the call stack because fn_dump_dblog creates its own thread scheduler and thread)

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

  1. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+2c6
    ResQueueBase::Dequeue+1cf
    DumpLogCoordinator::GetLogRecord+88
    CDBLogSTVF::GetRow+215
    CQScanTVFStreamNew::GetRow+d5
    CQScanFilterNew::GetRowHelper+8c
    CQScanSortNew::BuildSortTable+2a6
    CQScanSortNew::OpenHelper+c0
    CQScanNew::OpenHelper+41
    CQScanStreamAggregateNew::Open+30
    CQueryScan::StartupQuery+240
    CXStmtQuery::SetupQueryScanAndExpression+2bd
    CXStmtQuery::InitForExecute+34
    CXStmtQuery::ErsqExecuteQuery+36a
    CXStmtSelect::XretExecute+2f7
    CMsqlExecContext::ExecuteStmts<1,1>+400
  2. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+2c6
    ResQueueBase::Dequeue+1cf
    DumpLogCoordinator::WaitUntilLogBufferIsFree+125
    RestoreRedoMachine::DumpRollForward+242
    BackupLogRedoMachine::RedoSegment+200
    BackupLogRedoMachine::DriveRedo+2b1
    BackupOperation::RestoreDataFromMedia+195
    BackupOperation::VerifyRemainingBackupSet+38
    BackupOperation::VerifyBackupSet+12d
    BackupEntry::DumpLogVerify+7f
    SubprocEntrypoint+a59
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8