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(Books Online description: “Used to synchronize access to read-ahead operations during key range parallel scans.”)
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Added in SQL Server version:
Removed in SQL Server version:
Extended Events latch_class value:
Maps to the AM_KEY_RANGE_GENERATOR_READAHEAD map_value in sys.dm_xe_map_values.
The map_key value in sys.dm_xe_map_values is 15 in 2008 and 2008 R2, and 9 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):