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Re: Concept Question --- Redo Log Recycle

From: Ganesh Raja <ganesh_at_gtfs-gulf.com>
Date: 23 Nov 2001 23:13:18 -0800
Message-ID: <a8aed4.0111232313.1909287c@posting.google.com>


Hi,

Yes oracle reads the RBS to Rollback the changes that are still uncommited in the database.

Every Time i Issue a Commit a SCN is assigned to the Transaction. All Transactions in the Redo Which does not have a SCN are Rolledback using the RBS data.

Hopw i am Right.

Regards,
Ganesh R

"jane" <janeyiu_at_optonline.net> wrote in message news:<EjyL7.35760$636.6281420_at_news02.optonline.net>...
> 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 Sat Nov 24 2001 - 01:13:18 CST

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