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Transaction Log - LSN resets

  • January 11, 2012 at 5:04 am

    #391286

    Hi,

    We've just experienced something here where the LSN appeared to reset itself.

    i.e

    The LSN was going 1,2,3,4,5,6 up to 200 then we took a full backup, now I know this breaks the chain but I would expect the next LSN to be 201 or something, but it wasn't, it was 5.

    I was wondering if someone knew what triggers this reset of the LSN, I can understand it reusing the numbers after a long period of time but I wondered if it was documented anywhere what the triggers for this may be? I can't seem to find anything.

    Regards,

    Nic

  • January 11, 2012 at 5:12 am

    #1431711

    The LSN is in 3 portions. The VLF,the log block and the log record. Which one dropped down?

    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

  • January 11, 2012 at 5:13 am

    #1431712

    I shall find out now and let you know.

    Thanks,

    Nic

  • January 11, 2012 at 5:20 am

    #1431717

    p.s. The overall LSN won't ever decrease. If it does, SQL hard crashes on the spot, by design.

    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

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