That error message is thrown when you try to execute a differential backup on a database before a full backup was taken. I tested it creating a new database named MyLab and issuing the following command:
BACKUP DATABASE MyLab
TO DISK = 'C:\BackupSQL\testbackupdiff.dif'
Cannot perform a differential
backup for database "MyLab", because a current database
backup does not exist. Perform a full database backup by reissuing
BACKUP DATABASE, omitting the WITH DIFFERENTIAL option.
Taking a full backup before a differential is a prerequisite. The Create a Differential Database Backup doc says:
- Creating a differential database backup requires a previous full database
backup. If your database has never been backed up, run a full database
backup before creating any differential backups.
Since your full backups are scheduled to happen on Sundays, you're likely to see no error Monday. But you can configure your hallengren script with the option to change the backup type to avoid that situation on the future. From the hallengren doc:
Change the backup type if a differential or transaction-log backup
cannot be performed.
Y Change the backup type if a backup cannot be performed.
N Skip the backup if a backup cannot be performed. This is the default.
DatabaseBackup checks differential_base_lsn in sys.master_files to
determine whether a differential backup can be performed. If a
differential backup is not possible, then the database is skipped by
default. Alternatively, you can set ChangeBackupType to Y to have a
full backup performed instead.
Another possibility is that your full backup is using the
WITH COPY_ONLY option. See Copy-Only Backups doc:
A copy-only backup cannot serve as a differential base or differential
backup and does not affect the differential base.