Re: which way use to assign the rollback segment?

It's fewest transactions one with round-robin on them.

That is, if you have several segments with same amount of transactions, Oracle picks the "next" one after the last one used.

Which is, IMO, not the best thing for them to do, because, if there exists a large batch job, that runs several times during periods of low activity and which is not assigned to a specific rollback segment, it will grow all your, say, 16 rollback segments to be big, where you start considering setting optimal size ... I am afraid to continue :).

If Oracle would just pick the first rollback segment among those with least used segments, say, in the order they are specified in init.ora, it would skew the space usage for rollback segments towards the "first" rollback segments but I fail to see any bad consequences of this.

Regs
AK

"Howard J. Rogers" wrote:

> Yes, I am sure.
>
> The order in which the segments are listed in the init.ora is the order in
> which they are brought online. Not the order in which they are subsequently
> used.
>
> If what you say was true, how would we handle public rollback segments which
> don't get listed in the init.ora because they are brought online at startup
> automatically? No list, no use, presumably??
>
> So, no. It's not a round-robin algorithm, but a 'fewest transactions' one.
>
> And yes, set transaction use rollback segment blah over-rides that default
> behaviour.
>
> Regards
> HJR
>
> "Julio" <julio.negueruela_at_si.unirioja.es> wrote in message
> news:3DABFF53.E3AB6637_at_si.unirioja.es...
> > Excuse me, are you sure? I believed that Oracle Engine assigns it to the
> next available
> > rollback segment unless you explicitily assign one with "set transaction
> command". If you
> > define the rollback_Segments parameter with a list, then they will be
> assigned in the
> > order you specify in that list.
> >
> > "Howard J. Rogers" wrote:
> > >
> > > Nope. The rollback segment with the fewest number of active
> transactions.
> > >
> > > Regards
> > > HJR
> > >
> > > "y" <y_at_y.com> wrote in message news:3DA8B10C.B715DE59_at_y.com...
> > > > Oracle8i EE.
> > > > Suppose I defined 20 rollback segments. And most of time there are 100
> > > > active transactions. When a transaction need the rollback segment to
> > > > save the before-image, In which way Oracle Engine determine to pick up
> > > > one rollback segment for this transaction? Round Robin?
> > > > TIA!
> > > >
> >
> > --
> > Julio Negueruela
Received on Wed Oct 16 2002 - 16:05:30 CDT