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Back up schedule for log backup (using Ola's scripts) as follows:

  • Start Time - 2AM
  • End Time - 11.59.59PM
  • Interval - Every 15 minutes.

On November 5th, all the back ups went as detailed above. Normally no log back up exists at 1AM, but on one of the servers after the 11:45PM back up there is a log back up at 1AM whereas other servers have log backups that start at 2AM.

My question is: why there is a back up at 1AM on one server, when all the other servers don't have a log backup at that time? Will this break the LSN?

When restoring do I need to restore 11:45PM then 1AM then 2AM and so on?

The LSN are given below

11 45pm Log- first LSN: 85246:1956:1, last LSN: 85246:3496:1

12.00 Full- first LSN: 85246:4241:180, last LSN: 85257:583:1

1 am log - first LSN: 85246:3496:1, last LSN: 86097:4867:1

2 am Log first LSN: 86097:4867:1, last LSN: 86105:2224:1,

2.15 am Log - first LSN: 86105:2224:1, last LSN: 86111:4864:

Any help will be greatly appreciated.

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  • Prior DST question leading up to this one: Daylight Saving Time Commented Nov 6, 2017 at 16:11
  • Should I ask the question there ?
    – SqlNovice
    Commented Nov 6, 2017 at 16:13
  • No, I was linking to it for context. Why did you revert my edits? Commented Nov 6, 2017 at 16:17
  • Just added November after 5th rest are there...i am new here sorry
    – SqlNovice
    Commented Nov 6, 2017 at 16:18

1 Answer 1

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Based on the LSNs in the log files, you should be fine.

If restoring from your full backup taken at midnight, you shouldn't need the 11:45 log file (it should be fully covered by the full backup); You'd restore:

  • the full backup
  • the 1AM log file
  • the 2AM log file
  • the 2:15 log file
  • and so on.

As to why a log backup was taken at 1AM? I can only speculate.

If there was no 2AM log backup on that server, it's at least remotely possible that the 2AM log backup managed to start before the system clock shifted the time to 1AM, and to record its activity after that happened. If that happened, when it went to set the time for the next run, it probably would have scheduled it for 2AM again, since it would see the time was (say) 1:01:07. I wouldn't say its likely, but I can't personally rule out the possibility (perhaps someone else can). To speculate even more wildly, if this happened on only one server, it could possibly be having some issues with it's clock chip. Is this server unique in any way (for instance, the oldest server in the farm)? Again, this is wild speculation, and I have nothing further to offer than the slim possibility.

More likely: is there a chance that there was an old job set up to take a log backup at 1AM on the first Sunday in November, or something like that?

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  • Thanks for your answers. there is no back u jobs at 1 am only integrity check happens every Sunday 1am. I am also in the same page as you as I believe there was a lag between the system clocks. Another Interesting thing is that on that servers there were 3 databases and among those two has 1 am back up taken and the other one after there is no 1 am back up..
    – SqlNovice
    Commented Nov 6, 2017 at 16:54
  • Note that the theoretical backup job I'm talking about would be one that would have existed since last November, might not have a name in sync with the normal names, and would literally be schedule to run once a year. If you have any doubts, double-check the last run timed of job to see if any ran in that timeframe. May be worth a double-check, just to be sure - as I note, of the two possibilities, it's the more likely one.
    – RDFozz
    Commented Nov 6, 2017 at 17:02
  • Checked the sql agent jobs and there is only two back up jobs that is Full and Log.....As long as my Back up chain is intact then I guess I am safe..Thank you
    – SqlNovice
    Commented Nov 6, 2017 at 17:22

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