(Republishing, or using this info in a commercial product/website, is prohibited without permission. All other uses are permitted. If in doubt, please ask.)
Description:
Unclear, but from the call stack, I think this latch class is when a thread is waiting for access to a copy of an object’s metadata.
(Books Online description: none)
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:
2008
Removed in SQL Server version:
N/A
Extended Events latch_class value:
The map_key value in sys.dm_xe_map_values is 145 in 2008 and 2008 R2, and 142 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):
- Generating or using a specified identity value
Abbreviated call stacks (list number matches known occurrences list):
- XeSqlPkg::latch_suspend_end::Publish+138
LatchBase::Suspend+16b8
LatchBase::AcquireInternal+415
CMEDSeqGen::AddGeneratedValue+1e0
CMEDProxyIdentity::AddGeneratedValue+2f
SetidentI2I4+13a
sqlTsEs.dll!CEsExec::GeneralEval+1a9
CQScanUpdateNew::GetRow+43d
CQScanXProducerNew::GetRowHelper+53
CQScanXProducerNew::GetRow+15
FnProducerOpen+57
FnProducerThread+8c3
SubprocEntrypoint+a7f
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+a8