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This wait type is when the log writer thread (or one of the log writer threads, on 2016+) is waiting for something to do (either log to flush or a write to complete).
(Books Online description: “Occurs while the log writer task waits for work requests.”)
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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 127 in 2008 and 2008 R2, and 131 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 wait type be a noticeable contention point.
This wait type is one that I usually filter out as a benign wait when doing wait statistics analysis.
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for some work to be entered into the log writer queue (either a log flush or a completed write)
Abbreviated call stacks (list number matches known occurrences list):