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This wait type is when a thread is running an online index operation and is blocked by other operations while waiting for the long-term Intent Shared lock. In this case, the WAIT_AT_LOW_PRIORITY option has been specified and the MAX_DURATION time has not yet expired.
You can read more about the WAIT_AT_LOW_PRIORITY option here.
(Books Online description: “Occurs when a task is waiting to acquire an Intent Shared (IS) lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.)”)
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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 938 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.
I have not seen this wait type be a noticeable contention point.
The duration of each wait of this type will be at most what the MAX_DURATION option is set to for the online index operation, after which either the online index operation will abort or it will force those operations blocking it to roll back (resulting in an LCK_M_IS_ABORT_BLOCKERS wait while the rollbacks complete).
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for the Intent Shared lock during an online index operation (same stack as for LCK_M_IS_ABORT_BLOCKERS except for a different location in the MDL::LockObjectLocal function)
Abbreviated call stacks (list number matches known occurrences list):