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TRACE_CONTROLLER

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Description:

This latch class is when a thread is waiting for access to the structure within SQL Trace that the controls traces.

(Books Online description: “Internal use only.”)

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Added in SQL Server version:

Pre-2005/2005

Removed in SQL Server version:

N/A

Extended Events latch_class value:

The map_key value in sys.dm_xe_map_values is 108 in 2008 and 2008 R2, and 105 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 latch be a point of contention.

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

  1. Waiting for access to add a new trace (in this case, adding the default trace during instance startup)

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

  1. LatchBase::Suspend+0x16b8
    LatchBase::AcquireInternal+0x415
    CTraceController::ClearRptMapForCurrentSpid+0x14a
    CSessionMgr::FAddSession+0x1c1
    PSessForSysTaskEx+0x55b
    CAutoSetupSQLExecContextsForInternalTasks::Setup+0x30
    CTraceBatchTask::Task+0xf3
    SOS_Task::Param::Execute+0x21e
    SOS_Scheduler::RunTask+0xab