Converting differential backups to full backups
If a differential backup runs and a full backup does not already exist for the database or filegroup, NetBackup can convert the backup to a full backup. Similarly, NetBackup can convert transaction log backups if a full backup does not already exist for the database. Enable this behavior with the keyword CONVERTBACKUP.
See Keywords and values used in batch files.
NetBackup only converts a differential backup if a full backup was never performed on the database or filegroup. If a full backup does not exist in the NetBackup catalog but SQL Server detects an existing full LSN, NetBackup performs a differential backup and not a full. In this situation, you can restore the full backup with native tools and any differentials with the NetBackup MS SQL Client. Or, if NetBackup expired the backup, you can import the full backups into the NetBackup catalog. Then you can restore both the full and the differential backups with the NetBackup MS SQL Client.
The agent checks to determine if a full backup was ever performed for each database. If no previous full backup exists, the backup is converted to a full as follows:
If you select a database for backup, the backup is converted to a full database backup.
If you select for the , the backup is converted to a full read/write filegroup backup.
If you select a filegroup for backup, NetBackup does the following:
If the filegroup is the default database filegroup, NetBackup converts the backup to a full filegroup backup.
If the filegroup is a secondary filegroup and a backup of the primary filegroup does not exist, NetBackup converts the backup to a partial full database backup. This backup contains the selected filegroup and default filegroup.
If the filegroup is a secondary filegroup and a backup of the primary filegroup does exist, NetBackup converts the backup to a full filegroup backup of the selected filegroup.
If you perform a partial differential backup, NetBackup does the following:
If no previous full backup exists for the default filegroup, NetBackup adds the filegroup to the backup and converts the operation to a full partial backup.
If a previous full backup exists for the default filegroup but a secondary filegroup in the files list does not have a full backup, NetBackup converts the operation to a full partial backup.
The CONVERTBACKUP option also detects if a full recovery database was switched to the simple recovery model and back to the full recovery model. In this scenario, the log chain is broken and SQL Server requires a differential backup before a subsequent log backup can be created. If NetBackup detects this situation, the backup is converted to a differential database backup.