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21GB DB creating 60GB log file after backup

  • July 23, 2016 at 2:10 am

    #400457

    Hi,

    As per title, I have a 21GB database with Simple recovery mode. Every night I do a full backup of the database but its creating a 60GB transaction log when this backup happens.

    Autogrowth size are set as 10% and unrestricted growth.

    Any recommendations on how to rectify this problem?

    Many thanks in advance

  • July 23, 2016 at 4:19 am

    #1891694

    The log can't be reused while a backup is happening, so it suggests that, at the time you do the backup, the DB is very active (or maybe running index rebuilds). Try backing up at a quieter 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

  • July 23, 2016 at 7:18 am

    #1891698

    Thanks Gila,

    I don't have any reindexing going on. I have the backup set for 3AM so I'll just bring it back a few hours to see if it helps.

  • July 23, 2016 at 7:29 am

    #1891700

    What you can also do, to narrow down the cause, is schedule a job to write the following into a table, during the backup process.

    SELECT name, log_reuse_wait_desc FROM sys.databases

    WHERE name = '<name of database that you are interested in>'

    That way you can see exactly what is preventing the log from being reused, no guessing.

    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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