Diff backup fails with error 3035 but log backup succeeds



  • We have a SQL Server 2014 Enterprise where the DIFF backups fail.
    This is the error message we get:

    Msg 3035, Level 16, State 1, Server sqltest, Line 1
    Cannot perform a differential backup for database 'database1', because a current database backup does not exsist. Perform a full database backup by reissuing BACKUP DATABASE, omitting the WITH DIFFERENTIAL option.

    After analysing the output of the following query we noticed that a third party tool was taking snapshot backups.

        select top 20 bs.type,bs.database_backup_lsn,bs.checkpoint_lsn,bs.backup_start_date,bs.is_snapshot,
        bs.is_copy_only,bs.user_name
        from dbo.backupset bs
        where bs.database_name = 'database1'
        order by backup_start_date desc
    

    According to https://blog.sqlauthority.com/2017/04/19/sql-server-msg-3035-level-16-cannot-perform-differential-backup-database-sqlauthority-current-database-backup-not-exist/ these tools use VSS to take a backup which is not a normal full backup.

    What I don't understand is why LOG backups succeed? To my knowledge, they are also based on the last FULL backup.
    Can somebody explain this difference to me?



  • A log backup is not based on the most recent full backup. It is based on the most recent log backup.

    I.e., you can "skip" a full or differential backup when you restore log backups, as long as you have an unbroken chain of log backups.

    As for your particular issue: Work with the backup software/vendor and see if you can make it perform the snapshot backups so they are seen as COPY_ONLY by SQL Server. Possibly a setting in your backup software.




Suggested Topics

  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2