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DBCC_CHECK_AGGREGATE

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Description:

This latch class is when a thread is waiting for access to the structure that controls a running DBCC consistency check.

(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 41 in 2008 and 2008 R2, and 35 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 noticeable contention point.

See the LATCH_EX wait type for more information about latches in general and how to troubleshoot them.

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

  1. Accessing the structure while in a loop processing pages to generate consistency checking facts

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

  1. XeSqlPkg::latch_suspend_end::Publish+138
    LatchBase::Suspend+16b8
    LatchBase::AcquireInternal+415
    CheckAggregateSingleInstance::GetNextFact+1df
    CTRowsetInstance::FGetNextRow+3c
    CQScanRmtScanNew::GetRowHelper+3b5
    CQScanXProducerNew::GetRowHelper+53
    CQScanXProducerNew::GetRow+15
    FnProducerOpen+57
    FnProducerThread+8c3