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You may encounter an Access Violation exception using Availability Groups (AG) in SQL Server 2017 and 2019, under the following conditions:

  • There are large log backups of the secondary replica (The size of each log backup may be measured in few GBs).

  • Primary and secondary replica transport and database level connections timed out and reconnected, causing the ongoing log backup to fail.

  • Primary replica may be experiencing a scheduler blocking pattern.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


This issue is fixed in the following cumulative updates for SQL Server:

About cumulative updates for SQL Server:

Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:


To workaround this issue, you may avoid:

  • Access violation if the log backup is executed on Primary replica.

  • Frequent transport and database disconnect and reconnect pattern (observed in the error log).


Learn about the terminology that Microsoft uses to describe software updates.

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