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

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