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Transaction Log - VLFs

  • January 25, 2016 at 10:41 pm

    #399624

    On a SQL Server, at any point of time, do all the transactions happening on the server will be written on multiple VLFs? Is it possible? In that case, how does the server determine what is the MaxLSN as the LSN is spanned over multiple VLFs?

  • January 26, 2016 at 1:57 am

    #1854366

    No. One at a time. The LSN is an always-increasing value, so if SQL starts using a VLF, it can't go back and write to an earlier one.

    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 26, 2016 at 7:05 am

    #1854433

    I you want to read up on this then here is a quality TechNet article by Paul Randal. Half way down the article is all about the Transaction Log and LSNs.. enjoy!

    https://technet.microsoft.com/en-us/magazine/2009.02.logging.aspx#id0060041

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