In article <36F8CD86.648A1AFE_at_capgemini.co.uk>,
Mike Burden <michael.burden_at_capgemini.co.uk> wrote:
> Agreed that redo logs aid recovery, but surely they are not essential. If you
> accept that in the event of a failure, you will restore to a cold backup, why
do
> you need the redo logs. If you don't back them up and you loose everything you
> can still go back to a cold back even without the redo logs. I have thought
> about putting redo and rollback segments into a RAM disk to prevent the disk
IO
> in certain situations (e.g. Development environment). I've already tried it
with
> Rollbacks in RAM which seem to work OK. If it all goes nasty you just restore
> and re-run. No roll forward necessary.
>
> It would be nice if you could turn either or both off and save on the
overhead.
> Hence three modes. This would be particularly useful for large overnight batch
> jobs where you do a cold backup at the end anyway. Because the job works
99.999%
> of the time you wish to take advantage of the fact by switching off redo and
> rollback and save on loads of IO.
>
> Just my thoughts. Anyone else care to comment. Are these features available in
> any other DBMS?
>
> I still think Oracle writes twice as much data to the redo logs than it needs
to
> because rollback info gets logged too. But that's another story.
>
Actually, in a way, you do have a choice, but Oracle makes you select this
option for every table and index you may want to create. If a table is not so
important that you wish to write to the redo logs, you can create it with the
NOLOGGING option, which will bypass writing to the redo logs.
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Received on Wed Mar 24 1999 - 10:10:55 CST
