Can I backup tran log on a principal db (ie. principal in a mirror)

  • Sorry if it's a dumb question. In a bit of a panic!

  • Yes, and you should be backing up the logs regardless of whether or not it's mirrored.

    Unless I'm misunderstanding your question..

  • Thanks. You're not misunderstanding. Sorry, it was a dumb question. I've just inhereted a mirrored pair & the tran log was full & the users were wailing & gnashing their teeth. I'm not familiar with the mechanisms of mirroring - reading up now!

    Looks like there are no backups at all on this system ... teriffic! Sorry to have bothered and thanks for the reply.

  • You have to take log backups. Mirroring means full recovery. Full recovery means that the log is only truncated (space marked reusable) when a log backup occurs. So no log backups, the log grows until it hits max size or fills the drive

    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
  • jessyb (9/27/2011)


    Thanks. You're not misunderstanding. Sorry, it was a dumb question. I've just inhereted a mirrored pair & the tran log was full & the users were wailing & gnashing their teeth. I'm not familiar with the mechanisms of mirroring - reading up now!

    Looks like there are no backups at all on this system ... teriffic! Sorry to have bothered and thanks for the reply.

    No such thing as a dumb question, only dumb decisions that come from not asking the question when you were unsure in the first place 🙂

    Gail's blog has more info on transaction logs and basic maintenance stuff than you'll likely ever need, so check it out once you get that log backed up and mirroring running smoothly.

  • Derrick Smith (9/27/2011)


    Gail's blog has more info on transaction logs and basic maintenance stuff than you'll likely ever need, so check it out once you get that log backed up and mirroring running smoothly.

    My blog doesn't, it's mostly execution plans, indexes and performance-related posts. My articles here are the admin-type.

    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
  • Thank you. Bit of a trauma just because I was unfamiliar with mirroring. Won't be caught out again.

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