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Re: Minimizing backup induced downtime

From: Alexander Skwar <>
Date: Fri, 13 Jul 2007 08:50:41 +0200
Message-ID: <>

joel garry <> wrote:

> On Jul 12, 2:31 pm, Alexander Skwar <>
> wrote:

>> ยท joel garry <>:
>> > Please see  Metalink Note:302615.1 RMAN and Split Mirror Disk Backups
>> > for how to keep the downtime very small and use RMAN to backup,
>> > keeping the Oracle and non-Oracle parts synced by splitting them both
>> > at once.  Maybe I still don't get it, but I tried.
>> I don't have access to Metalink, but I'll see if our Oracle
>> support can send me this document tomorrow. Thx.
>> It shows how to backup non-Oracle parts with RMAN? Interesting.
>> I hope they can send me this metalink document.
>> > Another odd thought, get directories of the non-Oracle files into a
>> > file, mount that external and CTAS into the db.
>> Hm. Interesting thought. How would I make sure, that the
>> directory-gone-file is always up to date? I guess this would mean, that
>> the app should also update this directory-gone-file when it modifies the
>> files in the directory? So I'd have to double the storage - once I need
>> to store the files as files in the vault directory and once as a
>> directory-gone-file?

> Well, hopefully a directory listing is smaller than your files :-)

You bet.

> That was just an off-the-top suggestion, implementing it is an
> exersize. But the key to that sort of scenario is diffs, and when to
> make them.

Okay. Got to think about that.

>>>>From where does RMAN/Oracle
>>>>pull the data about what has been done between 22:46 and 22:59,
>>>>if archive logs aren't available?

>>If that's somehow possible, then you really got me hooked on

> You need to read the basic manuals if you don't understand this.

I really don't understand how RMAN can recover something, which hasn't been backed up or that's no longer available.

> When
> you backup online, the files are in a fuzzy state. When you recover,
> logs are applied to make them unfuzzy. So with a PITR, you can
> recover until whenever you want.

Yep. I know.

> If the archived logs are not
> available, it is not possible.

Exactly. And that was my point. SB "informed" me, that I cannot restore/recover/"reget" anything from an EXP dump, which has been inserted/changed/deleted in the database, after the point in time, when the EXP was started. That's of course a given. My point now was, that the same thing holds true with RMAN backups or archived logs as well.

Let me quote SB: "ALL TRANSACTIONS AFTER YOUR SO-CALLED 'BACKUP' WILL BE LOST FOREVER." So we now finally got to the point, that we can agree that even when using RMAN his statement holds true.

> That is why you want to back them up,
> and that is why you want to not lose any after the backup.

It's not about losing something which has been backed up. It's about not having backed up something, as it has been created right after the time the backup finished.

> There are
> a number of scenarios where you need to restore where you haven't lost
> the archived logs.

Of course.

> For example, you lose a device that has data files
> on them. One of the data files has never been backed up. You can
> recover the data file and its data even so!

I know.

> I believe there is an
> example of this in the manual.

I'd think so, yes.

> Metalink access is really useful.

I know.

Alexander Skwar Received on Fri Jul 13 2007 - 01:50:41 CDT

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