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This wait is when a thread is part of a restore operation where there are multiple backup devices. The thread barrier is used to synchronize threads that are restoring parts of a single block of data from multiple streams; essentially all threads need to complete before they can progress to the next block.

(Books Online description: N/A)

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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 1209 in 2017 RTM. After 2017 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

Prior to SQL Server 2019, if an error occurs while a thread is reading from a backup file or writing to a database file, it is possible that this may cause all the other threads to be ‘hung’ waiting for this wait type, resulting in having to manually kill the restore. SQL Server 2019 catches this case and fails the restore correctly.

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

  1. TBD

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

  1. TBD