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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):
- Waiting for a mutex while initializing a DBCC CHECKDB parallel thread
Abbreviated call stacks (list number matches known occurrences list):
- 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