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Transaction Log Backup during Full backups

  • December 27, 2006 at 5:24 am

    #176217

    Hi

    I have a database backup whoch occurs every 12 hrs at 12:00 Am and 12:00 PM.I also have log backup

    every 15 min.The full backup usually takes a hour or so and i have noticed that the next log backup

    file is generated after the full backup is created.Can anyone tell me why does the transaction log backup not execute while

    the full backup is going on.

    thanks

  • December 27, 2006 at 6:35 am

    #680065

    Hi,

    First of all, you needn't cross post.

    Second...  A transaction log backup relates to the previous full backup.  If a full backup is in progress then you cannot have a transaction log backup (or a diff backup) occurring at the same time.  The full backup cycle consists of writing database pages to disk - this starts at a given point in time.  When the backup has finished writing pages to disk, SQL Server then, I believe, dumps the pages that have changed up until the end point-in-time of the backup so that a consistent point in time is obtained.  Obviously you could not have a transaction log backup occur in the middle of this, as far as backups are concerned, atomic process.

    Cheers, Ian

  • December 28, 2006 at 9:52 am

    #680307

    This is a limitation in SQL Server 2000. We call it the backup black hole. In 2005 you can do a tlog while a full is in progress to keep you within your sla's for backup and recovery.

    cheers,

    Wes

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