Doubt about Shrinking process , Rebiulding index and fragmenatation

  • hi i know that shrinking data base increase fragmentation , so logically shrinking data files would two result in fragmentation but does shrinking log file increases fragmentation. i hope answer is NO.

    Second question is rebuilding an index reduces fragmentation but it increase size of database.I have seen increase in size of log file but does data file size to increases . Again i hope ans is No.

    Plz correct me on this

  • anoop.mig29 (3/19/2013)


    hi i know that shrinking data base increase fragmentation , so logically shrinking data files would two result in fragmentation but does shrinking log file increases fragmentation. i hope answer is NO.

    Shrinking log file does not create any fragmentation.

    Second question is rebuilding an index reduces fragmentation but it increase size of database.I have seen increase in size of log file but does data file size to increases . Again i hope ans is No.

    Plz correct me on this

    rebuilding/re-organizing index is a fully logged operation, therefore your log will be growing during the time of rebuild/re-organize.

    SueTons.

    Regards,
    SQLisAwe5oMe.

  • Why are you shrinking the log file? If your backup method is Full then the logfile will truncate on backup.

  • Erin Ramsay (3/19/2013)


    Why are you shrinking the log file? If your backup method is Full then the logfile will truncate on backup.

    Full and Differential backups do not truncate (mark VLFs as reusable) the t-log. Only transaction log backups accomplish this when a database is using the BULK_LOGGED or FULL recovery models.

  • anoop.mig29 (3/19/2013)


    hi i know that shrinking data base increase fragmentation , so logically shrinking data files would two result in fragmentation but does shrinking log file increases fragmentation. i hope answer is NO.

    Index fragmentation, no. However, lots of shrink/grow/shrink/grow will cause log fragmentation. You shouldn't be regularly shrinking your logs. Once off, yes. Regular, no.

    Please read through this - Managing Transaction Logs[/url]

    Second question is rebuilding an index reduces fragmentation but it increase size of database.I have seen increase in size of log file but does data file size to increases .

    Yes it can. If there's not enough space in the database for the new index, the data file will grow.

    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
  • Lynn Pettis (3/19/2013)


    Erin Ramsay (3/19/2013)


    Why are you shrinking the log file? If your backup method is Full then the logfile will truncate on backup.

    Full and Differential backups do not truncate (mark VLFs as reusable) the t-log. Only transaction log backups accomplish this when a database is using the BULK_LOGGED or FULL recovery models.

    Learn something new every day...thank you, sir!

  • GilaMonster (3/19/2013)


    anoop.mig29 (3/19/2013)


    hi i know that shrinking data base increase fragmentation , so logically shrinking data files would two result in fragmentation but does shrinking log file increases fragmentation. i hope answer is NO.

    Index fragmentation, no. However, lots of shrink/grow/shrink/grow will cause log fragmentation. You shouldn't be regularly shrinking your logs. Once off, yes. Regular, no.

    Please read through this - Managing Transaction Logs[/url]

    Second question is rebuilding an index reduces fragmentation but it increase size of database.I have seen increase in size of log file but does data file size to increases .

    Yes it can. If there's not enough space in the database for the new index, the data file will grow.

    Hi Gail thanks for reply but whats log fragmentation is it hramfull??

  • Log fragmentation is described in the article I referred you to.

    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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