Differential and log backups fail after full backup

  • Hi All,

    Today I was setting up log shipping during which I realised that if a database has never been backup up and if the first backup issued is with the option Copy_only, the successive differential and log backups do not happen and throw the error

    like "Backup log cannot be performed as the full backup does not exist'

    Is this a bug in SQL server or some kinda restriction?

    Once a full backup w/o copy only option is issue and even though the backup is deleted and then a new backup with copy only is created, the subsequent log backups happen. I am assuming that this has something to do with firing up the LSN.

  • Implied by what a copy_only backup is.

    A copy_only full backup doesn't set the differential base and can't be a base for log backups. Hence if that's the only backup ever taken, both differential and log will fail just as if no backup had ever been taken.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass
  • krishna.vanne (9/8/2011)


    Once a full backup w/o copy only option is issue and even though the backup is deleted and then a new backup with copy only is created, the subsequent log backups happen. I am assuming that this has something to do with firing up the LSN.

    SQL has no way to know that you deleted the full backup. Do note that any differential backup you take is completely useless since the full has been deleted.

    Why would you take a full backup, delete it, then take another one with copy_only? Rather a waste of time.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass
  • Thanks for your reply. It was just a part of my testing that I deleted the full backup. I was surprised to see that errors got fixed all of a sudden and was debugging back to what I have done.

    I was banging my head why log shipping was failing and found that the backup script had the copy only option which was the culprit in this case. Few of the databases were being backup fine but few bombed.

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