Bufpoolsize and cache hit percentage on ADSM DB

I am running ADSM server 3.1.2.40 on AIX 4.3.2.0 with 512MB memory.
The ADSM DB size is 19GB, with 67.2% used.

I am trying to tune the Bufpoolsize so as to reach >98% cache hit
percentage, as recommended by Tivoli/IBM.

When I started, a few months ago, the value of bufpoolsize was 16K and we
had 75% cache hit %. By increasing bufpoolsize, I managed to get over 95% at
170000K.

Since then, I have had the following results (making changes every few
weeks):

Bufpoolsize = 170000 , cache hit % = 95.28.
Bufpoolsize = 190000 , cache hit % = 94.77
Bufpoolsize = 220007 , cache hit % = 93.26

All results are after many millions of DB accesses. A UNIX admin has told me
that the machine has no memory paging problems.

Does anyone have any idea why this is happening?
Am I getting better performance with the larger buffer pool even if the
cache hit % is lower?

Please cc me on list replies as I subscribe to the digest version.

Thanks,

Jonathan  Shalev
IDC Computing / Systems Engineering
UNIX Server Platforms
Intel Israel (74) Ltd.
Jonathan.Shalev AT intel DOT com
Phone: +972-4-865-6588, Fax: +972-4-865-5999