CHECK_TABLES_INITIALIZATION

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Description:

This wait type is when a parallel thread for a DBCC CHECKDB (or related) command is initializing and waiting for a mutex that another initializing thread is holding.

(Books Online description: N/A)

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Added in SQL Server version:

2016

Removed in SQL Server version:

N/A

Extended Events wait_type value:

Maps to the CHECK_TABLES_INIT map_value in sys.dm_xe_map_values.

The map_key value in sys.dm_xe_map_values is 1107 in 2016 RTM. After 2016 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 a mutex while initializing a DBCC CHECKDB parallel thread

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

  1. SOS_Task::PostWait+0x6f
    WaitableBase::Wait+0xb7
    TAutoMutex<SOS_Mutex,1>::GetAccess+0x103
    CheckTables::InitializeInternal+0x3c
    CheckAggregateSingleInstance::GetNextFact+0x28d
    CTRowsetInstance::FGetNextRow+0x3c
    CUtRowset::GetNextRows+0xa0
    CQScanRmtScanNew::GetRowHelper+0x41f
    CQScanXProducerNew::GetRowHelper+0x63
    CQScanXProducerNew::GetRow+0x15
    FnProducerOpen+0x5b
    FnProducerThread+0x80b
    SubprocEntrypoint+0x1201
    SOS_Task::Param::Execute+0x231
    SOS_Scheduler::RunTask+0xad