Re: AIX 4.2 and Oracle 7.2/7.3 SGA/PGA and virtual memory

Hi,

Well, you maybe right. Actually the SGA is now sized 52MB of 128MB, which as I can measure it, is the largest it can be in the environment in question. As you ask, what is a large SGA??? I never had heard about the 30% before, but as a rule of thumb it makes sence to me (of course depending on environment). Thanks a lot for your answer.

Regards
Jens Wartenberg

WARTENBERG                      |     People
Industri Data  -  Denmark       |     that make a difference
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IBM RS/6000 - IBM AIX - Oracle  |     For industrial needs
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Ki wrote:
>
> Jens Wartenberg <wartenberg_id_at_ibm.net> wrote in article
> <3320034A.68EB_at_ibm.net>...
> > Anton Dischner wrote:
> > >
> > > Hi,
> > >
> > > i did performance measurements with different SGA sizes on different
> > > CPUs.
> > >
> > > IBM RS6000 5xx and SMP, SGI, HP. Oracle 7.x
> > >
> > > I found that a small SGA performs better than a big SGA !!
> > > I believe this is because filesystem caching performs better than
> > > Oracle SGA-caching.
> > >
> > > Give a small SGA a try!
> > > Make Oracle-blocksize as big as possible.
> > >
> > > Kind regards,
> > >
> > > Toni
> > >
> > > --
> > > A. Dischner, SGI&AIX sysadmin, Oracle DBA | Don't let friends
> > > Institut fuer Klinische Chemie | use WinDose
> > > Klinikum Grosshadern | Just say NO.
> > > Ludwig Maximilians Universitaet Muenchen, GER |
> > > Marchioninistr.15 81366 Muenchen 49-89-70953202 |
> >
> > This surprises me a lot!!!!
> >
> > I thought that because Oracle is able to distinquish between which reads
> > are likely to be reused (lru-algorithms, indexed reads etc.), it would
> > be a benefit to give the ram to Oracle.
> >
> > I am presently increasing the sga (db_block_buffers, shared_pool_size)
> > and has decided to test the users view on performance by reverting to
> > the previous settings for a few days.
> >
> > I will report what the users believe (ram to AIX or Oracle).
> >
> > Regards
> >
> > Jens Wartenberg
> > Wartenberg Industri Data
> > Denmark
> >
>
> Hi,
>
> I read in several places that SGA should take 30% of real memory available.
> probably mr. dischner used a larger sga size (which caused swapping) and
> found out that
> a smaller one behaves better, while mr. wartenberg used a small sga in the
> first place, just to find out that enlarging it is payfull.
>
> Just an hypothese .
>
> I'm working excellently with 30% Real memo sga.
>
> yours,
>
> Muli Koppel
Received on Wed Mar 12 1997 - 00:00:00 CST