Re: why aren't ORA-1555 errors MORE frequent?

Of course, that makes perfect sense. Thanks for the explanation.

Richard Kuhler

Richard Foote wrote:
>
> "Richard Kuhler" <noone_at_nowhere.com> wrote in message
> news:gewC9.15096$2z1.6176523_at_twister.socal.rr.com...
> > "Howard J. Rogers" wrote:
> >
> > <snip>
> >
> > > > Interesting. You're saying that the cleanouts themselves have to be
> > > > written to a RBS? I can't envision any reason for this. Why is this
> > > > done? This also seems to imply that a pure SELECT could run out of
> > > > rollback, right?
> > >
> > > You can certainly get 1555s when no-one is doing anything other than
> pure
> > > selects, true enough. They are incredibly hard to demonstrate, however,
> > > being as rare as hen's teeth.
> > >
> > > Regards
> > > HJR
> >
> > Actually, I was thinking that if the cleanouts have to be written to a
> > RBS then the SELECT could actually get "ORA-1650 Unable to extend
> > rollback segment" or similar, right?. More significantly, I'm trying to
> > figure out why cleanouts would have to be written to a RBS to begin
> > with.
>
> Hi again Richard,
>
> Part of the "clean-out" involves updating the header with the SCN of the
> original transaction (or the SCN as close as Oracle can reproduce it so they
> we know for the sure that the original transaction was *no later* than the
> recorded SCN). Note that this overwrites the previously recorded SCN.
>
> From a read consistency point of view this previous SCN is a vital link. If
> the current SCN is not early enough for a consistent read, we need to
> determine what was the value of the previous SCN. Hence the need to record
> this info in the RBS.
>
> Cheers
>
> Richard
>
> >
> >
> > Thanks,
> > Richard Kuhler
> >
Received on Wed Nov 20 2002 - 12:39:02 CST