FIX: Error occurs when you try to create a differential backup on secondary replica in SQL Server 2017

Applies to: SQL Server 2017 on Windows

Symptoms


Assumethat you use SQL Server 2017. When you try to create a differential backup on a secondary replica, you receive a message that indicates that the command is running and maysucceed:
 
BACKUPDATABASE WITH DIFFERENTIAL successfully processed {X} pages in {Y} seconds
 
Differentialbackups are not supported for secondary replicas. After you apply this fix, the correct error message is displayed:
 
Msg3059, Level 16, State 1, Line LineNumber
ThisBACKUP or RESTORE command is not supported on a database mirror or secondaryreplica.
Msg3013, Level 16, State 1, Line LineNumber
BACKUPDATABASE is terminating abnormally.

Note Currently, SQL Server does not allow differentialbackup on a secondary replica because it can’t modify the differential bitmappage. This is because the database is read-only. Additionally, copy-only transaction log backups arenot allowed on a secondary replica. To maintain backup consistency, this hotfixprevents running a copy-only differential backup on a secondary replica.

Status


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

Resolution


This issue is fixed in the following cumulative update 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:

References


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