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

Memory Issue

vnobien — Mon, 26 Mar 2007 23:52:54 GMT

Hi,

HP-UX Server B.11.11 have 12GB Memory, lockable ~ 9.3GB run Oracle Applications 11.5.9 with SGA = 800 MB, PGA = 500 MB. When I check memory, it consume ~ 93%!!!

#swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 117 3979 3% 0 - 1 /dev/vg00/lvol2
reserve - 3691 -3691
memory 9458 8821 637 93%
total 13554 12629 925 93% - 0 -

Please help me to explain what consume memory? (Attachment file include: top, swapinfo, ipcs, kmtune).
Thanks.

Re: Memory Issue

Rasheed Tamton — Tue, 27 Mar 2007 01:24:29 GMT

Hi,

Your swap space value (4GB) is not sufficient enough. The recommendation is to have 2 X Physical memory. In your case (since pseudoswap is used) it should be 24GB swap disk space.

Did you finetune your kernel parameters according to Oracle requirements.

Please check the below kernel values.
dbc_max_pct (set it to 20 )
dbc_min_pct (set it to 5)

Regards,
Rasheed Tamton.

Re: Memory Issue

Jollyjet — Tue, 27 Mar 2007 01:36:03 GMT

Little more information will help.

What's your buffer cache parameters?. If you are using default of 50% dbc_max_pct, then it will be a over kill. What are your max_dbc_pct, nbuf and bufpages settings? You can use 'kmtune -l -q ' to get this information.

Re: Memory Issue

vnobien — Tue, 27 Mar 2007 02:33:26 GMT

Hi,

I will increase swap more but I want to know what consume 8821 HP-UX system memory? How to calculate memory (I don't have glance)?

#kmtune -l -q dbc_max_pct
Parameter: dbc_max_pct
Current: 50
Planned: 50
Default: 50
Minimum: -
Module: -
Version: -
Dynamic: No

NBUF = 0 and BUF_PAGES = 0

I think that the dbc_max_pct parameter is only partial of high memory issue because my DEV server HP-UX B.11.11 RAM: 5GB (same kernel parameters with PROD Server) where can still run 2 Oracle Apps Instances (clone from Oracle PROD) (max memory Consumption ~ 7-8GB).
Thanks.

Re: Memory Issue

vnobien — Tue, 27 Mar 2007 21:05:54 GMT

Hi,

Please help me to explain memory issue: 2113220K is real memory?

#top
Memory: 2113220K (1441196K) real, 5253816K (3724692K) virtual, 136988K free

Thanks

Re: Memory Issue

goldboy — Tue, 27 Mar 2007 21:35:48 GMT

you can use the "dmesg" command to see the phisical memory at the bottem of the results.

Tal

Re: Memory Issue

Bill Hassell — Tue, 27 Mar 2007 22:03:22 GMT

> Please help me to explain memory issue: 2113220K is real memory?

The memory numbers from top are useless. With 12 Gb of RAM, 800 megs for Oracle is way too small. Your DBA can significantly improve performance with a larger SGA.

dbc_max_pct is far too large for 12gb RAM - change it to 10 (10% or 1200 megs). ninode is still a formula and outrageously high. Wipe out the formula and set it to 2048.

You'll get much more useful shared memory information with ipcs -bmop rather than plain ipcs. With this much memory and Oracle as a database, you definitely need Glance to properly manage this system's performance.

Re: Memory Issue

vnobien — Tue, 27 Mar 2007 22:26:27 GMT

Hi Bill Hassell,

I intend to increase PGA from 500MB to 2GB and SGA to 1.2GB after adding more swap (10GB).

#swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 102 3994 2% 0 - 1 /dev/vg00/lvol2
reserve - 3639 -3639
memory 9458 8854 604 94%
total 13554 12595 959 93% - 0 -

Please explain why Memory is 94% (8854MB)? What consume my HP-UX memory?
Thanks

Re: Memory Issue

Tom Henning — Wed, 28 Mar 2007 05:52:48 GMT

ynobien
The dbc is the dynamic buffer cache, which is an area of memory set aside for the use by the kernal. The default setting for HP-UX systems for the dbc maximum, as mentioned by Bill Hassell, is 50. This allocates a maximum of half your memory to the kernal's use in buffering I/O. The buffer cache, although it is called dynamic, tends to grow to until the maximum is reached. So for your system, you probably have 6 GB of memory devoted to the buffer cache.

As recommened by Bill Hassell, you should lower this kernal parameter to 10, or even 5 or 6 (600 MB to 840 MB).