Kernel Tuning

[ian nelson_2]

Is it possible to tune a kernel parameter in HPUX11i with a formula that doesn't rely on another kernel parameter?

A customer i am working with at the moment is running a number of Oracle 8i servers. The SGA (system global area) configured for Oracle relies on the HPUX kernel parameter shmmax being larger than the SGA value.

A problem arises when the SGA value, which contains data and control information for an oracle instance is resized. Resizing causes Oracle to give out of memory messages and the shmmax parameter must be altered to fix this. Would it be possible to configure shmmax with a formula that reads the SGA value and configures the parameter accordingly?

[Jerome Baron]

Hi,

shmmax is a dynamic kernel parameter. You can set this by using kmtune kmtune -s shmmax=Ox???? .
You can use this to set shmmax in a script with the SGA size.
# kmtune -l -q shmmax
Parameter: shmmax
Value: 0x40000000
Default: 0X4000000
Minimum: -
Module: -
#kmtune -s shmmax=0x4000000
#kmtune -l -q shmmax
Parameter: shmmax
Value: 0x4000000
Default: 0X4000000
Minimum: -
Module: -

Does it respons to your answer ?

Regards,
Jerome

[Ian Dennison_1]

How dynamic is the SGA and how likely to be resized? How large is the growth of the SGA?

I personally would be hesitant to make UNIX try and jump through all sorts of hoops for an issue that revolves around Database design.

Having said that, shmmax is a dynamic variable, that should be able to be changed on the fly. Investigate the 'kmtune' and possibly try it on a trash-and-burn box.

Share and Enjoy! Ian

[John Palmer]

If you know that programs/users are not going to take advantage, why don't you just set shmmax to a large value and then forget about it?

The maximum for a 32bit kernel is 0x40000000 (1Gb) and for a 64 bit kernel 0x40000000000.

Regards,
John

[Wodisch]

Hi,

to second John: SHMMAX is a *limit* not a table or anything like that.
You can use it to restrict some process of allocating too huge amounts of shared memory at once, but you don't have to!
Set it to the maximum of RAM your box can be equipped with and that's it.

FWIW,
Wodisch

[Steven E. Protter]

For smooth operation of the oracle servers, you whant to push the shmmax parameter as far as you can go.

Oracle is a huge shared memory eater. Like potato chips or something. You want all the shared memory queues to be liberal, especially if you are running any other database on the box.

Take a look at an ipcs command while your oracle is up.

Oracle appears capable of eating anything you feed it, to continue the food analogy.

Out of memory errors can be causes by lots of things.

Make sure the java version is 1.2 or 1.3 and is certified. java 1.4 is not certified by Oracle.

This document shows the latest Oracle patches, some of which could impact you.

http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_database_id=NOT&p_id=43507.1

Document id 43507.1

Here is the good part.

HP-UX 11.11 =========== 6. C++ runtime libs Current Revision of Patch: PHSS_26946 - s700_800 11.11 HP aC++ -AA runtime libraries (aCC A.03.37) Patch in latest Support Plus Patch Bundle? Yes, as PHSS_22898. 5. asyncio driver patch - slow database startup with large SGAs Current Revision of Patch: PHKL_25506 - s700_800 11.11 asyncio driver patch Patch in latest Support Plus Patch Bundle? Yes, as PHKL_25506. 4. ONC/NFS General Release/Performance Patch Current Revision of Patch: PHNE_26388 - s700_800 11.11 ONC/NFS General Release/Performance Patch Patch in latest Support Plus Patch Bundle? Yes, as PHNE_26388. 3. ld and linker tools cumulative patch Current Revision of Patch: PHSS_26560 - s700_800 11.11 ld(1) and linker tools cumulative patch Patch in latest Support Plus Patch Bundle? No. 2. libc cumulative patch Current Revision of Patch: PHCO_27740 :s700_800 11.11 libc cumulative patch Patch in latest Support Plus Patch Bundle? Yes, as PHCO_25452. 1. libc cumulative header file patch Current Revision of Patch: PHCO_24402 :s700_800 11.11 libc cumulative header file patch Patch in latest Support Plus Patch Bundle? Yes, as PHCO_24402.

Check those patches and look for more current ones in itrc.

Build a big patch bundle and install them all at once. That's how I did it, saved time.

P

[ian nelson_2]

Thanks everyone for your advice. I particularly like Jeromes idea of creating a script to do the job.

The ini.ora file holds various values that determine the SGA size. Using these values shmmax can be tuned to the correct value. The idea is that this can be run when any database tuning takes place.

Many thanks once again!

Ian