Re: Online backup: Backup online redologs?

"Randall Roberts @filer.org>" <randall<nsp> wrote in message news:3b0b036e_1_at_news.pcmagic.net...
> >>I'm not saying that I agree with everything they are doing (I don't see
> >>why anyone would use an OS copy of the controlfile).
>
> If you're serious...
>
> You need a backup control file in case of the loss of all online copies of
> the control file.

You most certainly don't. All you need is the *trace file* backup of the control file, which will merrily re-create all required copies without the need for a resetlogs. There is no requirement to perform such recovery with binary (ie, "O/S copies") copies of the controlfile. Hell, if you're any good with the 'create controlfile' syntax, and have your database structure well-documented, you don't even need the tracefile backup -you can just type the relevant commands at a SQL prompt in the nomount stage (not to be recommended, though, I agree).

>Also, to do point in time recovery to recover a dropped
> tablespace, you need to use a backup controlfile from before the
 tablespace
> was dropped.
>

That's the one exception I allowed for in my original post -where the controlfiles you've got don't describe the logical and physical database you want (ie, it's got a reference to a tablespace missing). It's the *only* occasion I can think of where the binary backup has benefits over and above what the tracefile version can do. That said, it is actually quite hard to 'accidentally' drop a tablespace -given that you'd likely have to use both the 'including contents' and the 'cascade constraints' clauses!

> Forgive me if I've missed the point of your statement.
>

Does the above make any more sense to you now? Trace files = good. Binary backups = OKish, but not likely to be used very often. Trace files=no need for resetlogs. Binary backups = compulsory resetlogs. Trace files = good for other things (cloning, renaming a database). Binary backups = about as useful for other things as a stunned mullet in a vegetarian automotive hardware store.

Of course, if you use RMAN, things become rather different again....

Regards
HJR
> Best!
>
> Randall
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Received on Tue May 22 2001 - 21:41:32 CDT