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This latch class is when a thread is waiting for access to the lock that controls communication between threads running backups on an availability group secondary. The RESQUEUE refers to a thread-safe hash table for processing the messages.
(Books Online description: N/A)
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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 155 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 heard anecdotal evidence that this latch can show up as a contention point when there a high disk latencies on the availability group secondary where the backup is being performed. Look for ASYNC_IO_COMPLETION and BACKUPIO waits occurring too, as these wait types occur when reading from a data file and writing to a backup file during a backup, respectively.
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):
Abbreviated call stacks (list number matches known occurrences list):