Re: Oracle Recovery Scenarios

On 19 Aug 2003 01:33:16 -0700, Ed <ed_zep_at_ntlworld.com> wrote:

> Hi.
>
> Does anyone know of a list of Oracle disaster/recovery scenarios with
> their solutions. What I have in mind is a flow diagram with something
> like
>
> "control file missing" -----> solution
>
> Ideally it could fit on a single sheet. This is sounding a naive
> question, but should the worst happen it would be great to not have to
> look through manuals.
>
> Does anyone know of a document like this?
>
> Thanks.
>
> Ed.
>

No, and sorry to say, I wouldn't tell anyone about it even if I did. You simply can't do recovery with flow diagrams. There's a billion and one possible variations, and no flow diagram is ever going to cover all eventualities.

Seriously: the only way to master backup and recovery is to understand the mechanisms Oracle uses to ensure database synchronisation. If you can visualise where your data files are at, what agrees with what, and what the application of redo does to things, then it really becomes relatively straightforward. I'm not saying that *you* are trying to avoid this sort of low-level understanding by producing flow charts, but if your junior were to try and follow a generic flow diagram without understanding what is going on, it'll be a recipe for total disaster except in the simplest of cases.

There might well be legal implications to producing such a document, too. If I lost hundreds of thousands of dollars because a flowchart-follower had just trashed my database, I'd be gunning for the flowchart producer. Probably.

If you really, really want mindless recoveries, then use RMAN. The commands don't need searching in the manual (at least not in 9i: restore database; recover database; ...works nearly every time!).

Seriously: try and understand what is going on during normal database operations, and then it becomes painfully obvious what needs to happen during recoveries. The commands aren't that taxing, either: recover database, recover datafile, recover tablespace and recover database until TIME | SEQUENCE | CANCEL. That's about it, really, unless you are getting into the really exotic stuff... and then no amount of flowchart is going to help you.

By the way, you'll never need anything very complex to know how to deal with a "control file missing" situation, because if you multiplex your control files, as you're supposed to do, the solution is simply to copy one of the duplicates back into the slot vacated by the missing one. ;-)

Regards
HJR Received on Tue Aug 19 2003 - 05:06:53 CDT