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Description:
This latch class is when a thread is waiting for access to the DBMRedoManager object that manages replaying of log records on a database mirror.
(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:
Maps to the DB_MIRRORING_REDO_MANAGER map_value in sys.dm_xe_map_values.
The map_key value in sys.dm_xe_map_values is 73 in 2008 and 2008 R2, and 67 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):
- Replaying a portion of transaction log on the mirror database
And many more similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):
- XeSqlPkg::latch_suspend_end::Publish+138
LatchBase::Suspend+16b8
LatchBase::AcquireInternal+415
DBMRedoManager::SubmitLogSegment+65
LsMgr::ProcessSegment+1b4
LsMgr::ProcessLogStream+79e
LsMgr::ProcessLogStreamResponse+6e
LsWorkRequest::Execute+47
LsWorker::ThreadRoutine+152
LsWorker::ThreadRoutine+1c7
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+a8