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This wait type is when the main parallel redo thread on an Availability Group replica needs to access the list of transactions that are being redone. Most of the time this list is accessed by the other parallel redo threads and this wait does not occur. This wait is part of normal parallel redo 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 1133 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.
This wait type is one that I usually filter out as a benign wait when doing wait statistics analysis as it is documented as not being indicative of a performance issue.
You can read more about parallel redo in this blog post.
Known occurrences in SQL Server (list number matches call stack list):
Abbreviated call stacks (list number matches known occurrences list):