Re: Oracle 8i Migration

"Dimitris Andrakakis" <dandrakakis_at_REMOVETHISmyrealbox.com> wrote in message news:<cd82ti$2sbb$1_at_ulysses.noc.ntua.gr>...
> > You should probably research COMPRESS=N and look into proper backups.
> > exp is not a recommended solution for backups, although it is good for
> > other things, including some backup redundancy.
>
> Well that's a disaster-scenario backup, and we've used it several times with
> success. Roughly, the procedure is this:
> -Hard disk crashes
> -Get new hd
> -Install OS from scratch, service packs, updates etc. The server in question
> does nothing but Oracle.
> -Install Oracle, same version (8i)
> -IMP the backup file.
>
> Thanks for the (COMPRESS=N) tip ! Do you think it'll be (a lot) faster ?
> Like 50% or so ?

Compress comes from the days when it was thought that putting all the data in a single extent when importing would increase performance, the idea being that the disk head could suck up contiguous data faster when reading the table (and older Oracle had extent limits). For most situations, this idea is not only discredited, but works against modern administration methodologies. Most people recommend making initial=next these days, for various reasons you could google for on this newsgroup. You probably won't notice any performance change due to using compress=n, but you may if you fix all the other problems that are likely if you don't know about basic Oracle features, like extent management and being able to recover transactions after a disk crash and such (not a flame, just my observation). It may be a lot faster to recover from a proper backup (even a cold one) than import, since in the scenario you describe you hardly have to do more than copy files. Oh, one case where you might notice a performance difference on imp is if you have a large table with many indices - your rollback will need to contain more than (the number of indices times the size of the table) at one time.

The dizwell.com faq among many others explain about extents.

There also have been ocassional bugs in exp/imp, check for additional patches that may be necessary towards the end of 8.1.7.x.

>
> > There is some safety in being supported.
>
> It sure is, and I'm not the one that'll say "go on your own". But there are
> some cases where really you need to. I suppose that, on Elias' case, there's
> only one server in the house and it has (for reasons irrelevant to Oracle)
> to be upgraded.

I'd be interested in knowing such reasons for Win2K. Oracle traditionally hasn't played well with others on Windows. I'd need to see some really, really strong reasons for a sole production box to be unsupported.

jg

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