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This wait type is when Query Store is loading its data for a database during startup of that database. This can occur after a crash, failover, or regular SQL Server startup, and the more Query Store data there is, the long the waits will be.

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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 988 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.

Other information:

By default, Query Store will synchronously load all its data for a database during database startup and this will prevent queries from running until the load has completed. If there is a lot of Query Store data, this can effectively prevent the database from coming online for many seconds or minutes, which can be problematic in high-uptime systems. If that is the case, you can enable trace flag 7752 to cause Query Store to asynchronously load the data and not block queries from running, as documented by Microsoft here.

Known occurrences in SQL Server (list number matches call stack list):

  1. TBD

Abbreviated call stacks (list number matches known occurrences list):

  1. TBD