Limitations of backups of availability groups
Note the following limitations for backups of availability groups (AGs):
NetBackup does not support the following types of backups for AG databases:
Snapshot backups of filegroups or files
Instant Recovery backups
VMware backups
Backups of non-readable secondary replicas
NetBackup can only back up databases in a replica when you allow user connections for the replica.
If a secondary replica is the preferred replica and it is non-readable, the backup fails. If a secondary replica is not the preferred replica, NetBackup skips the backup of that replica.
SQL Server does not support the following types of backups on a secondary replica:
Full backups
If a full backup takes place on a secondary replica, NetBackup converts the full backup to a copy-only backup.
Differential backups
Backups of this type result in a failed backup.
Copy-only transaction log backups
Backups of this type result in a failed backup.