Re: RMAN questions...

"Steve Howard" <stephen.howard_at_us.pwcglobal.com> wrote in message news:6d8b7216.0311121333.2af1fa7b_at_posting.google.com...
> Hello All,
>
> Oracle 8.1.7.4.1
> HP-UX 11.11
>
> We are moving towards using RMAN, and I would like to know the
> following:
>
> Let's say for arguments sake that I created a full database backup
> from RMAN one week ago, and then did incremental RMAN backup's nightly
> as well as archived all of my redo logs. Using exactly the same setup
> on another machine (OS, database version, size, etc.) , I do a full
> hot backup one week ago, and then archive all of my redo logs for the
> following week.
>
> Assuming all other things are equal (I understand the other benefits
> of RMAN such as block corruption detection, backing up only changed
> blocks, etc.), which one _should_ take longer to restore? Is RMAN
> architected to reassemble a database without restoring the full
> backup, then running through all of the incrementals, and then
> applying all of the archived redo? If so (or if not), is this much
> faster than just doing a regular old hot backup? Or is this apples
> and oranges?

Apples and oranges, I think.

Nothing in this world is "architected", by the way -that's why we have the word "designed".

But whatever, RMAN will indeed need to restore the relevant components of the full backup, and apply the incrementals to it to bring it up to date (it couldn't really be any other way, if you think about it). That's if it decides to do it that way in the first place. It *may* decide to simply restore the week-old full backup and roll the whole lot forward using the archived redo logs, which is exactly the way it will be forced to do it in the second of your scenarios. You can't say for sure, because RMAN works out the optimal plan at the time. In general, it prefers full backups to incrementals, disk-based backups to tape-based ones, and image copies to backupsets.

So, if the question is: "is RMAN designed to optimise recovery operations?", the answer is yes.

Which will be quicker? In general, I'd place bets on RMAN to recover faster than a manual recovery. And without so much faffing around with mis-typed O/S commands, too. But that could just be my fingers.

Regards
HJR Received on Wed Nov 12 2003 - 15:47:17 CST