topic Re: Memory upgrade in Operating System - HP-UX

Memory upgrade

Claude Fortin — Mon, 07 Apr 2003 19:04:24 GMT

We have a L2000 with 1 gig,
and we want to upgrade it to 3 gigs,

What kernel parameters we have to change?

Re: Memory upgrade

James R. Ferguson — Mon, 07 Apr 2003 19:21:16 GMT

Hi:

No changes are absolutely required. A better question would be what limitations (i.e errors reported) have you already encountered? A posting of your current configuration ('kmtune -l') along with a description of your server's function (e.g. database engine, mail server, etc.) might would lead to a better answer.

Regards!

...JRF...

Re: Memory upgrade

Michael Tully — Mon, 07 Apr 2003 23:05:15 GMT

The only change I would look at, and this is of course after the installation of your additional RAM would to be to look at your buffer cache usage. As a guide this should end up being around 300Mb. So utilising this as a percentage which is how the kernel sees it you should have your buffer cache setting at 10%
The kernel parameter is 'dbc_max_pct' and the minimum, setting could be 2%, 'dbc_min_pct'

Re: Memory upgrade

Michael Steele_2 — Tue, 08 Apr 2003 04:32:42 GMT

Note your nfile, nproc, ninode and maxusers parameters.

A very nice, yet complex, white paper appears under /usr/share/docs/mem_mgt.txt which discusses kernel parameters as related to physical memory. Also note the swap discussion.

This link had a lot to say and also brought up dbc_max_pct and dbc_min_pct concerns:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x155e87dc4d7dd5118ff00090279cd0f9,00.html

Re: Memory upgrade

Ravi_8 — Tue, 08 Apr 2003 04:57:09 GMT

Hi,

No need to change any kernel parameters for RAM upgrade

Re: Memory upgrade

Ovid Saveluc — Wed, 09 Apr 2003 04:07:39 GMT

Michael is absolutely right about dbc_max_pct, allocating more than 300-400 MB for buffer cache can negatively impact the performance.
There may be a whole bunch of parameters related to app/DB tuning, such as semaphores, shared memory, etc (after all I'm assuming you bought more memory to be able to support more users, more DBs/apps or maybe improve apps performance).
And don't forget to add more swap...

Cheers,
Ovid.