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(Books Online description: “Used to synchronize the first allocation for an append-only storage unit.”)
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Added in SQL Server version:
Removed in SQL Server version:
Extended Events latch_class value:
The map_key value in sys.dm_xe_map_values is 22 in 2008 and 2008 R2, and 17 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.
Known occurrences in SQL Server (list number matches call stack list):
Abbreviated call stacks (list number matches known occurrences list):