Re: Concept Question --- Redo Log Recycle

Thanks Howard,
right, no rollforward necessary.

>The rollback needed to reverse the uncommitted changes is thus readily
> available.

So you mean Oracle, in reco mode, reads the RBS to undo the changes ?

Can Oracle figure out - from the redo logs - the scenario I described and proceed to fix the database ?

jane

> The point is that it doesn't need to roll forward. Those dirty buffers
were
> flushed, together with their rollback blocks, when you switched logs. The
> rollback needed to reverse the uncommitted changes is thus readily
> available.
>
> Regards
> HJR
> --
> Resources for Oracle: http://www.hjrdba.com
> ===============================
>
>
> "jane" <janeyiu_at_optonline.net> wrote in message
> news:NIlL7.28121$636.5030654_at_news02.optonline.net...
> > I'm puzzled about the following scenario.
> > This question is about the inter-workings of online redo log files,
> > DBWn, CKPT...on 8i.
> > Pls point out anything I said wrong below.
> >
> > NOARCHIVELOG mode, have a HUGE rollback segment,
> > doing LOTS of modifications, SELECTs, but NO COMMITS.
> >
> > My question is:
> > Online redo files will be reused (yes ?), thus CKPT will happen
> > and dirty blocks with UNCOMMITED CHANGES in buffer will be
> > flushed/written to disk (yes ?).
> >
> > System crashes now.
> >
> > So what happens after instance is back up ?
> > Since the redo logs have been reused....
> > How exactly does Oracle roll-forward and undo the
> > UNCOMMITED changes to the disk ?
> > Read from RBS ?
> >
> > Pls be as specific as u possibly can.
> > Really appreciated !
> >
> > jane
> >
> >
> >
> >
> >
> >
>
>
Received on Fri Nov 23 2001 - 14:28:20 CST