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Newbie Restore Question - LSNs

  • March 9, 2009 at 10:59 am

    #201219

    I am working through my self-education of SQL backup / restore functionality etc...

    I have a question about LSNs. I understand the importance of Log Sequence Numbers and I have a pretty good grasp on the differences in backup strategies and types of backups. So, the following is curious:

    I created a test backup set which includes 1. A Full BU, 2. A Diff BU, 3. A Trn Log BU, and 4. Another Trn Log BU.

    I noticed that the LAST LSN for the Diff bu is the same as the first LSN for the next trn log bu, and the same for the trn bu and next trn bu. However, the last LSN for the Full BU and the first LSN for the Differential BU (which was taken after a few transactions) is not the same. I kind of expected it to be...

    Please advise, what am I missing?

    Thanks,

    Nick

  • March 9, 2009 at 12:09 pm

    #956295

    My guess is that what you are seeing is due to the use of the differential bitmap in the differential backup process. The differential backup header will contain the DatabaseBackupLSN which does correspond to the FirstLSN in the full backup.

    Not exactly an answer but I hope that it provides a bit of insight into what you are seeing.

    David

    @SQLTentmaker

    “He is no fool who gives what he cannot keep to gain that which he cannot lose” - Jim Elliot

  • March 10, 2009 at 7:10 am

    #956750

    Thanks... just a curiosity as I'm learning.

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