Shared pool 'perm' behaviour

From: Connor McDonald <hamcdc_at_yahoo.co.uk>
Date: Wed, 21 Mar 2001 16:49:43 -0800
Message-ID: <F001.002D42BA.20010321161529@fatcity.com>

Anyone observed this on their platform ? (Observations below are from Sun, v8.1.6 and 8.1.7)

Based on various things I've seen on the web, immediately after startup I would expect about half the shared pool to "kept aside" by Oracle (in the
'perm' area) and only released as memory comes under
pressure.

So to prove this assertion, I set 'shared_pool = 40m', and ran the following immediately after startup:

select ksmchcls, sum(p.ksmchsiz) tot
from sys.x$ksmsp p
group by ksmchcls;

KSMCHCLS TOT

-------- ----------
R-free      2000000
R-freea          40
free       16541304
freeabl     2514628
perm       21760488
recr         701904

which is what I would expect (ie about 50% in the
'perm' area)

So far so good... But then, if I bump up 'shared_pool' to 70m, then I see

KSMCHCLS TOT

-------- ----------
R-free      3500000
R-freea          40
free       60401700
freeabl     2524560
perm        6409504
recr         682552

thus all of a sudden, there is minimal 'perm', and virtually all of the memory is now deemed 'free'.

The switch over point seems to be somewhere around 68m.

Can anyone shed any light on this ??

Cheers
Connor

Connor McDonald
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Received on Wed Mar 21 2001 - 18:49:43 CST