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PREEMPTIVE_COM_COCREATEINSTANCE

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Description:

This wait type is when a thread is waiting for a call to CoCreateInstance to create a new COM object.

(Books Online description: “Occurs when the SQLOS scheduler switches to preemptive mode to create a COM object.”)

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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 387 in 2008 and 2008 R2, 435 in 2012, and 451 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. Creating a COM object, in this case while running the sp_testlinkedserver procedure

And other similar call stacks.

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

  1. SOS_Task::PopWait+bc
    SOS_Task::AutoSwitchPreemptive::~AutoSwitchPreemptive+72
    DBCoCreateInstance+b2
    COledbConnect::PdatiniGetInProcService+b6
    COledbConnect::PdatiniGetService+b2
    COledbConnect::CreateSession+8c4
    COledbConnect::GetSession+38b
    SpTestLinkedServer+241
    CSpecProc::ExecuteSpecial+25b
    CXProc::Execute+14e
    CSQLSource::Execute+90e