Re: quick hot backup question...

If you're doing O/S online backups, then there's no need for a preliminary checkpoint, because that's precisely what the 'begin backup' command forces (at least for the datafiles of the tablespace involved).

The one about a preliminary log switch (presumably because you are about to copy the archives) is always a curious one. Lots of people do it, and I've never really understood why. Usually the justification is that without it, you are short of the current redo log, so you may lose data. There's something to that, I suppose. But it's also usually (so I find) because people view a backup as an isolated event, whereas the truth of the matter is, of course, that what you don't backup tonight you will backup tomorrow. So if there's a bit of current redo left unbacked up, who cares?? You'll get it when tomorrow's backup is performed, and in the meantime there's no possible risk of data loss because you've multiplexed your online redo logs, and then mirrored them with hardware RAID. Haven't you?? ;-)

The other thing that mystifies me about forcing a log switch in order to get an archive of the current log is that it only makes another log the current log. So you can *never* really be completely and utterly up-to-date with redo copies, unless you stop all your users doing things: there'll always be a new piece of current redo which you haven't backed up today. Hence cold backups, of course.

That said, a log switch does no real harm -except induce a performance-hitting checkpoint.

Regards
HJR

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"Glen A Stromquist" <gstromquist_at_nospamyahoo.com> wrote in message
news:jpMn8.11561$EV.366849_at_news1.telusplanet.net...


> In my online backup scripts I don't do a logfile switch or force a

> checkpoint before copying the datafiles.

>

> Is this  recommended by Oracle?

>

> I'm wondering if I overlooked something when writing my scripts, I have

used


> my online backups on occasion to create a clone db, so I know they "work"

> the way I'm doing it now, but I guess  it can't hurt to build in a logfile

> switch and/or force a checkpoint as part of the script as well.

>

> Curious to hear what others do regarding this....

>

>

> cheers!

>

>