T log back up

  • Hi Experts,

    I have a doubt about full and T log backup,

    Today when I was working on one of my prod server I found that one of my database backup is getting failed due to some space issue. So, I cleared the space and re-ran the job manually. But here I got a doubt that when the full backup is under process there was a T log got generated and the time stamp if I compare it is matching the previous T log (as we configured the T log for every 15 minutes. So, the last was at 12:30 and the recent was at 12:45 and I re-ran the full backup at 12:38) so, my doubt is will the full backup have the data of a recent T log or it’s a new one. The time stamp after completing the full backup was 12:53 and the recent T log was done at 12:45.

    Please let me know how it works..

  • Query msdb.dbo.backupset, inside that table are a number of columns related to LSN's, you can then match the LSN numbers into the order that they would be required for restoring.

  • A full backup is consistent at the time it completes, so in this case it would contain the changes held in the 12:45 log backup.

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  • Full backups and transaction log backups are disconnected after the very first time you run a transaction log backup. You can pick any given full backup and use any set of transaction log backups to perform the restore. The only trick is, the transaction log backups have to be linked.

    Now, full backups and differential backups are directly linked. If you take a full backup without using the COPY_ONLY command, then that backup becomes the base for the next differential, but transaction logs do not work that way at all.

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  • Thank You All for your reply, I was in doubt whether the recent Full backup of the db will contain the info of the recent T log, Now it got clarified.

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