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Just as the Books Online description says below. Group commit means that fewer log block flushes/copies occur when using availability groups.
(Books Online description: “Transaction commit processing is waiting to allow a group commit so that multiple commit log records can be put into a single log block. This wait is an expected condition that optimizes the log I/O, capture, and send operations.”)
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Added in SQL Server version:
Removed in SQL Server version:
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 866 in 2012 and 885 in 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.
If you see this wait type is becoming prevalent and your transaction throughput is dropping, you can do the following:
- Enable trace flag 9546 to disable group commit
- Set your own maximum group commit threshold (the default is 10ms), as described in KB 4565944
Known occurrences in SQL Server (list number matches call stack list):
Abbreviated call stacks (list number matches known occurrences list):