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Changing @@SERVERNAME causes SQL Server Backups to Fail for AlwaysOn Availability Group

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One of customers changed the value returned from @@SERVERNAME.  SQL Server works no problem, however an unexpected behavior appeared.  Changing the value for @@SERVERNAME, caused the backups to fail.

Looking at the maintenance jobs, found all jobs completed successfully and without issues.  However, upon looking at the database’s statics it states no backups completed.

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Because the database in question is part of AlwaysOn Availability Group (AG); SQL Server executes sys.fn_hadr_backup_is_preferred_replica to determine if the backup should take place on the current node.  However, it returns value of 0 for all databases, if the preferred replica is set.  Because, the script makes a check that is running on the server that is preferred.  It does this by comparing the value to @@SERVERNAME to value of replica_server_name in sys.availability_replicas.  Because value will never match, it skips the database on both primary and secondary replica.

I have created a Microsoft Connect article (link); asking this little bit of information to be added to Books Online article (link).  There was a request submitted by Ola Hallengren (Blog | Twitter), which was closed as Won’t Fix (link).   Please vote!

This post is cross posted on my SQLCAN Blog, MSDN Blog, and SQL server Consultation blog.