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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)
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Added in SQL Server version:
Removed in SQL Server version:
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.
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):