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This wait can occur infrequently after a bottleneck was encountered by the main parallel read thread on an Availability group replica (i.e. after a PARALLEL_REDO_FLOW_CONTROL wait occurred.) 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 1134 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):