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 Implications of changing server time zone

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mmrtech
Starting Member

10 Posts

Posted - 2011-09-28 : 12:29:46
I'm preparing to migrate two SQLServer 2000 databases to a new server (retiring old hardware) and just noticed that the current server is set to Central Time, even though the server is actually located in the Eastern Time Zone. The new server has the correct time zone selected, but I'm worried that the difference will cause issues when I attempt to restore from backups onto the new server. The tlog files that I copied from old to new show lastmodifieddates in the future!

Thanks in advance for any suggestions.

Matt

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-09-28 : 12:33:09
that will definitely have an issue. All jobs etc that depends on system date will also get affected.

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SQL Server MVP
http://visakhm.blogspot.com/

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russell
Pyro-ma-ni-yak

5072 Posts

Posted - 2011-09-28 : 13:33:30
I don't think the file dates will be an issue at all when restoring the backups to the new server.

The only issues you'll have is scheduled job times suddenly being an hour later. You'll also have an hour with no transactions.
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visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-09-28 : 13:38:17
quote:
Originally posted by russell

I don't think the file dates will be an issue at all when restoring the backups to the new server.

The only issues you'll have is scheduled job times suddenly being an hour later. You'll also have an hour with no transactions.


what if at later they've have to restore to point in time and tries to identify the logs based on file name timestamp?

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http://visakhm.blogspot.com/

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mmrtech
Starting Member

10 Posts

Posted - 2011-09-28 : 15:41:05
I elected not to change the time zone on the old server, but did restore from the data and log backup files. There were no jobs scheduled during the migration time period, so I don't think we missed anything.

Russel, what did you mean about having an hour with no transactions? Were you thinking that SQLServer would ignore "future" transactions when restoring the tlog backup?
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russell
Pyro-ma-ni-yak

5072 Posts

Posted - 2011-09-28 : 20:49:18
Changing a server from Central to Eastern makes it advance an hour, not the other way around.

So if your computer clock suddenly goes from 4 to 5, then you'll have zero transaction for the hour between.

I was recently in a situation where it was the other way -- we migrated data from eastern time zone to pacific, and almost forgot to account for the time difference, when comparing sales east coast vs west coast. Wasn't a big deal once I remembered, but would've been ugly if I hadn't.

Changing the clocks back to earlier shouldn't present many real challenges unless you're doing time comparisons. Then you need to add the hour(s). And jobs that are supposed to run only once a day, make sure the switch is in a window where they won't run twice, or disable sql agent for an hour.
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mmrtech
Starting Member

10 Posts

Posted - 2011-09-28 : 23:00:20
I wouldn't have changed the time on the server, only the time zone. When I originally checked it, the clock in the system tray displayed 12:15, which was the correct time on the East Coast at that moment.

However, I copied new tlog backup files to another East Coast machine that was correctly configured and the timestamps on them was in the future because the machine configured for East Coast time considered files written at 12:15pm Central to have been written at 1pm Eastern. Net result, at 12:15pm Eastern, I see files on an East Coast machine timestamped 1:15pm Eastern

Thanks for the help and suggestions everyone. I didn't mean to argue the point at such length; only hoped to illustrate for future occurrences.
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