topic Memory Woes in Operating System - HP-UX

Memory Woes

Adrian Sobers2 — Fri, 24 Sep 2004 07:15:51 GMT

We are having a persistent memory leak of some sort on our HP-UX box running 11.11. It is a production server that hosts one production database (Oracle 8.1.7.4) 64-bit. Here are some stats:

machine has 2GB physical RAM, 4GB swap
oracle has 225MB total SGA

Right now there is only 330MB or so RAM free. After applying some patches yesterday afternoon and rebooting the free RAM was 1.3GB. This morning I come in and it's back to square one it seems (330MB) free.

Only major application on this server is Oracle. Is there anything else I should look for to help solve this problem? Any help would be greatly appreciated.

Re: Memory Woes

Rita C Workman — Fri, 24 Sep 2004 07:31:33 GMT

I'm no performance expert...but Oracle is a hungry beast, and 8.1.7 running your apps at 64 bit will chew up a good chunk of that 2Gb of RAM.

I would first put some more memory in the box.

Rgrds,
Rita

Re: Memory Woes

Zinky — Fri, 24 Sep 2004 07:33:31 GMT

How much buffer cache do you have allocated/

sysdef|grep pct

After your reboot, your system will initially have that memory free but as aplications (orace) start then other memory eaters will come into play. Filesystems get used and if you have the default dbc_max_pct of 50%, then 1GB will be used for filesystem and other caching already.

330MB free should still be "plenty" for a 2GB system. So everything is just about right... and your assumption of a memory leak may beunfounded.

Re: Memory Woes

John Palmer — Fri, 24 Sep 2004 07:33:45 GMT

What makes you think that you've got a problem? 330Mb free out of 2Gb is a lot of free memory!

It sounds to me as though you may have the kernel parameter max_dbc_pct defaulted to 50. This will allow the buffer cache to extend to 50% of available memory (1Gb in your case).

I'd be looking to reduce max_dbc_pct to 15 (300Mb) and significantly increasing the Oracle buffer cache in the SGA in order to improve Oracle performance.

Re: Memory Woes

Adrian Sobers2 — Fri, 24 Sep 2004 07:37:06 GMT

Thanks for the information. I think the memory leak idea is indeed unfounded. Thanks again.

Re: Memory Woes

Adrian Sobers2 — Fri, 24 Sep 2004 07:40:17 GMT

closed