DATABASE_MIRRORING_CONNECTION

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Description:

This latch class is when a thread is waiting for access to the structure that encapsulates low-level communication for a database mirroring session.

(Books Online description: “Internal use only.”)

Questions/comments on this latch class? Click here to send Paul an email, especially if you have any information to add to this topic.

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_CONNECTION map_value in sys.dm_xe_map_values.

The map_key value in sys.dm_xe_map_values is 76 in 2008 and 2008 R2, and 70 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. Sending one of the once-per-second pings to make sure the mirroring partner is accessible
2. Acknowledging a log stream buffer has been received
3. Acknowledging a message that was sent from the mirroring partner

And many more similar call stacks.

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

1. XeSqlPkg::latch_suspend_end::Publish+138
   LatchBase::Suspend+16b8
   LatchBase::AcquireInternal+415
   DbmTransport::SendNoFlowControl+5c
   DbmConnection::SendSSBMessageNoWait+185
   DbmConnection::SendPing+3ad
   LsConnectionStateMachine::OpenedAction+b2
   LsStateMachineBase::PostEvent+1d7
   LsStateMgr::ProcessEvents+113
   DbmDatabaseStateMgr::MasterThreadRoutine+303
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+a8
2. XeSqlPkg::latch_suspend_end::Publish+138
   LatchBase::Suspend+16b8
   LatchBase::AcquireInternal+415
   DbmConnection::SendStreamAck+a0
   DbmStream::Receive+263
   LsBuffer::Receive+40
   LsMgr::ProcessLogStream+314
   LsMgr::ProcessLogStreamResponse+6e
   LsWorkRequest::Execute+47
   LsWorker::ThreadRoutine+152
   LsWorker::ThreadRoutine+1c7
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+a8
3. XeSqlPkg::latch_suspend_end::Publish+138
   LatchBase::Suspend+16b8
   LatchBase::AcquireInternal+415
   DbmConnection::SendMessageAck+13e
   DbmConnection::ProcessReceiveMessage+124
   LsStateMachineBase::PostEvent+1d7
   LsStateMgr::ProcessEvents+113
   DbmDatabaseStateMgr::MasterThreadRoutine+303
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+a8