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This wait type is when a thread is waiting for access to the list of dirty pages during parallel redo on an availability group replica. This wait type can become prevalent on a replica where there is a lot of read activity on tables that are heavily updated on the primary replica.
(Books Online description: N/A)
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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 1127 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 very similar to the DPT_ENTRY_LOCK wait, but that wait is more common when there are a few pages that are being updated constantly.
Anecdotal evidence is that using indirect checkpoints might help to alleviate this.
On some servers running builds before SQL Server 2016 SP1 CU2, this wait type is the symptom of a crippling bottleneck during redo of transaction log records on an AG replica. If you are experiencing this, you can turn on trace flag 3459 using DBCC TRACEON (3459, -1), or adding it as a startup trace flag using the Configuration Manager, to disable parallel redo on that instance.
Known occurrences in SQL Server (list number matches call stack list):
Abbreviated call stacks (list number matches known occurrences list):