Re: ROLLBACK_SEGMENTS definition

Hi Howard,

Oh thank goodness, we disagree on something (that sound you hear is me jumping around the room whilst ripping up my airline ticket to Tasmania :)

Public vs. Private Rollback Segments

If I have 8 rollback segments I want to put online (because that's what tuning the system has ultimately determined is most appropriate), what are my options ? List them in the ROLLBACK_SEGMENTS parameter (note only the one Hrishikesh :) which lets face it is not too hard, or use a bit of mathematics (admittedly not most strongest point) and set the TRANSACTIONS and TRANSACTIONS_PER_ROLLBACK_SEGMENT appropriately.

At this point, not a huge amount of difference I admit.

But what if I specifically want my huge rollback segment online that my large transactions have need with the SET TRANSACTION USE command. How can I guarantee that it's one of the selected public rollback segments that go online with your suggestion. You can't.

What if I have a number of tablespaces for my rollback segments (perhaps for the above reason, perhaps for others) and I want a number from a particular tablespace or none from another etc. to go online, how can I control this with public. You can't.

Public rollback segments in my way of thinking only really make sense in an OPS environment, but even then I would prefer the manageability available with private.

Not a flame (take the jacket off), just a slight scorch with my cigarette lighter :)

Regards

Richard
"Howard J. Rogers" <dba_at_hjrdba.com> wrote in message news:ag2g4q$tht$1_at_lust.ihug.co.nz...
>
> "Hrishikesh Mehendale" <hrishikesh_mehendale_at_persistent.co.in> wrote in
> message news:ag1eaf$idt$1_at_news.vsnl.net.in...
> > Hi,
> >
> > I'm having a weird (?) problem, as follows:
> >
> > In my init<sid>.ora file, I have specified the following lines:
> >
> > ROLLBACK_SEGMENTS = RBS1
> > ROLLBACK_SEGMENTS = RBS2
> >
> > When I shutdown/startup the database, both (RBS1, RBS2) come online.
> >
> > However, if the lines are changed to either of
> >
> > rollback_segments = RBS1
> > ROLLBACK_SEGMENTS = RBS2
> >
> > ------ or -------
> >
> > ROLLBACK_SEGMENTS = RBS1
> > rollback_segments = RBS2
> >
> > only the second segment (RBS2) comes online (case sensitive ??)
> >
>
> Shouldn't be. Sure there isn't another line (even a blank one) between
them?
>
> If there isn't, then I suppose you ought to get the 'discoverer of the
> obscure bug of the month' award. But it's not really Oracle's fault... the
> standard advice is that if one parameter is repeated elsewhere in the
> init.ora, then the second version of it prevails. So in fact, what's wrong
> is your *first* example where you appear to have two versions of
> ROLLBACK_SEGEMENTS and they are *both* respected.
>
> In other words, the standard way of referencing multiple rollback segments
> is "rollback_segments=(X,Y,Z)", on one line.
>
> Frankly (and I don my flame-prrof suit here), I've given up worrying about
> all the rollback segment nonsense (and I'm not talking about 9i's
automatic
> undo, either). I just stick the word 'public' into every 'create rollback
> segment' statement, and watch them bring themselves online at startup
time,
> without referencing them in the init.ora at all:
>
> create public rollback segment R01 tablespace RBS;
>
> I've found no difference between a public and a private rollback segment
in
> day-to-day usage, except the convenience of being brought online
> automatically. The only thing to watch is setting the TRANSACTIONS and
> TRANSACTIONS_PER_ROLLBACK_SEGMENT init.ora parameters, which affect how
many
> of the blighters get brought online at startup. But they are single
paramete
> rs, taking simple arguments each. So it shouldn't be too hard to script
> something to adjust them.
>
> Regards
> HJR
>
>
>
> > However, doing this:
> >
> > rollback_segments = RBS1
> > rollback_segments = RBS2
> >
> > brings both segments online.
> >
> >
> > I'm facing this problem on Oracle 8.1.7 EE for Solaris (8.1.7.1.0) and
for
> > Linux (8.1.7.0.1).
> >
> > Any ideas on (a) what I'm doing wrong (b) how to solve this?
> > My problem is I have to add extra rollback segment(s) to a possibly
> > existing declaration in the init<sid>.ora file through a script.
> >
> >
> > Thanks
> > Hrishikesh
> >
> > --
> > Hrishikesh Mehendale
> > Member of Technical Staff
> > Persistent Systems, Pune.
> > http://www.persistent.co.in/
>
>
Received on Thu Jul 04 2002 - 18:51:40 CDT