Re: ROLLBACK_SEGMENTS definition

"Richard Foote" <richard.foote_at_bigpond.com> wrote in message news:S55V8.27742$Hj3.85775_at_newsfeeds.bigpond.com...
> 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.
>

You *can* mix public and private segments, you know ;-) If you've got this sort of mixed-load requirement, then get Oracle to bring the 'oltp' ones online automatically, and bring the special humungous ones online yourself/via the init.ora.

> 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.
>

Then sort your tablespaces out! You should have made one rollback segment tablespace comprised of a number of datafiles, spread around the place, so that the I/O is evenly distributed no matter which ones Oracle wants to bring online.

> 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.
>

I think they make a huge amount of sense in any 'standard' environment. As soon as you've got peculiar requirements, then yes, you need extra management control. The beauty is that you can have both, as needed.

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

You don't smoke! Owwww!!!

Regards
HJR
> 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 - 19:04:43 CDT