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  1. #1
    Join Date
    May 2009

    Unanswered: Possible to recover data from differential dumps w/missing intermediate full dumps?

    I have a client with MS SQL server 2005. They have been backing up their SQL server to our online backup service. The schedule they specified was:

    Full backup every Saturday at 4am
    Differential every day (including Saturday!) at 4am

    The backup software didn't flag this clearly bogus schedule. (I'm taking that issue up with the software vendor). What it appears to have done is allow the full backup to start, at least enough to cause the DB server to believe a full backup had been performed at 4am. But the full backup file did not get saved and uploaded to the online backup server.

    The first full backup worked, in October 2008. The subsequent differential backups worked each night. But after the first week, the differentials are
    against the most recent "phantom" full dump, not the one existing full dump from October.

    This continued for 6 months. We have about 200 differential backups and one full backup. We don't have any of the intervening full backups that
    we need to make the differential backups make sense.

    Last week the database server got trashed. Now we are trying to restore the database. We can load the full dump, and the first few differentials. But the first differential after the first "phantom" full dump can't be loaded. (I don't have the error message handy, sorry). Microsoft tech support has told them there's no way to recover.

    Does anyone have any ideas for a way to recover? If I take the full from 10/21, then restore the diff's up to 10/24 (Friday 4am), can I somehow force it to apply the diff from 10/25 (Sat 4am) and beyond?

    As I write this, I'm realizing that all data from Fri-4am to Sat-4am would be missing. That may make it totally nonsensical.

    If anyone has any ideas, I'd appreciate them. Thanks,


  2. #2
    Join Date
    Feb 2004
    In front of the computer
    Provided Answers: 54
    No, there is no way to recover all of your data from these backup files. You may be able to recover significant amounts of the data if you engage the services of a data recovery team, but that will be hugely expensive (at least six figures).

    The problem is that restoring the differentials is not possible due to key log data that would be missing. I don't know of any automated process that could restore those backup files for you, that would take manual effort and even then it may not be possible to restore all of the data.

    In theory, theory and practice are identical. In practice, theory and practice are unrelated.

  3. #3
    Join Date
    May 2009


    Thanks for the confirmation. I had a feeling that would be the case.


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