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(Books Online description: “A query on object(s) in a readable secondary database of an Always On availability group is blocked on row versioning while waiting for commit or rollback of all transactions that were in-flight when the secondary replica was enabled for read workloads. This wait type guarantees that row versions are available before execution of a query under snapshot isolation.”)
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Added in SQL Server version:
Removed in SQL Server version:
Extended Events wait_type value:
Maps to the HADR_WAIT_FOR_TRANSITION_TO_VERSIONING map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here).
The map_key value in sys.dm_xe_map_values is 849 in 2012 and 868 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.
Known occurrences in SQL Server (list number matches call stack list):
Abbreviated call stacks (list number matches known occurrences list):