(Republishing, or using this info in a commercial product/website, is prohibited without permission. All other uses are permitted. If in doubt, please ask.)

(Back to main page…)


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)

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:


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.

Other information:

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):

  1. TBD

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

  1. TBD