topic Re: dbc_max_pct ???? in Operating System - HP-UX

dbc_max_pct ????

luigi coco — Thu, 17 Jun 2004 06:07:45 GMT

my system is in this way composed:

current value dbc_min_pct 5
current value dbc_max_pct 50

SYSTEM DATA
===========
HOSTNAME: omdbsrv1
SYSTEM: 9000
MODEL: 9000/800/SD64000
RISC CHIP: N/A
PA VERSION: N/A
SYSTEM ID: 941141999
CPU SPEED: 875 MHz
CPUS: 8 active processor(s)
MEMORY: 16368 Mbytes of memory.
HP-UX VERSION: B.11.11 64 Bit

how should I set dbc_max_pct having these memory values, considering that on this sever is running only a Oracle db????

Total VM : 5.53gb
Active VM: 4.48gb
Sys Mem : 2.96gb
Buf Cache: 7.99gb
User Mem: 4.23gb
Free Mem: 824.4mb
Phys Mem: 16.0gb

what are the best Kernel values for a
DB-Server ???

thanks....

Re: dbc_max_pct ????

Jeroen Peereboom — Thu, 17 Jun 2004 06:21:23 GMT

L.S.

check this link:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=467288

400MB seems to be a nice dbc size.

You may also use the more options search at the top of the screen for dbc_max_pct in the HP-UX forum.

JP.

Re: dbc_max_pct ????

Ashwani Kashyap — Thu, 17 Jun 2004 06:48:26 GMT

dbc_min_pct 5 and dbc_max_pct 10 should be fine for this .

Re: dbc_max_pct ????

Steven E. Protter — Thu, 17 Jun 2004 07:17:11 GMT

Your current settings will result in a lot of cpu expensive changes in memory allocation.

dbc_min_pct=5
dbc_max_pct=7

That is what our shop uses for 8.1.7, 9.2.0 and servers with an environment mixed between the two. It works well.

SEP

Re: dbc_max_pct ????

Rita C Workman — Thu, 17 Jun 2004 07:46:40 GMT

...oh that default value....somebody wake up in HP and change that turkey !!

Change your dbc_max immediately....best to start with 7-10 % and for db_min go with maybe 5%. You can tune after that.

For what are the best kernel settings, this will vary on what your DB is requiring.
Check with your DBA and find out a couple things...like how has he configured his init.ora? how many processes is he setting up for? what is his SGA size?....
The answers to these (and others) tell you what to set your shmmax and semm* settings to, just for a start.
But you'll also want to look at other things.
This should get you a start...and then you can post more and get help.

Rgrds,
Rita
...8 proc w/16gb Memory....nice !

Re: dbc_max_pct ????

Rgomes — Thu, 17 Jun 2004 07:50:04 GMT

Hi,

dbc_min_pct 5 and dbc_max_pct 10 would be fine. Our production servers are running fine with those kernel parameter.

regards,
Richard

Re: dbc_max_pct ????

Francesco Campalastri — Thu, 17 Jun 2004 07:51:46 GMT

Hi,
I usually set it this way:

dbs_min_pct = 2
dbs_max_pct = 5

It means from 320 MB to 800 MB for you.

Francesco

Re: dbc_max_pct ????

Geoff Wild — Thu, 17 Jun 2004 07:58:26 GMT

Yes - you want between 350 to 700 MB for DBC_MAX - I would set yours to 7% with dbc_min_pct at 5%.

On my 10GB ram systems, I have it set to 8%.

Oracle does it's own buffering - so it won't use it...

With 50%, you are reserving half your ram !!!

Change it to 7 and that will free up ram for Oracle.

Rgds...Geoff

Re: dbc_max_pct ????

Bruno Ganino — Thu, 17 Jun 2004 08:15:58 GMT

About your dbc_max_pct and dbc_min_pct i think that the setting dc_max_pct is too high.
Use sar -b and %rcache, if it is minor of 90% not need to set hight.

hth
Bruno

Re: dbc_max_pct ????

Jose Mosquera — Thu, 17 Jun 2004 09:07:54 GMT

Hi,

This is a % value. The recomendations are from 5% to 10% depends on the total amount of memory in your system. The minimun value must be 300MB, then you can try to put a low percentage. Almost all of my boxes have:
dbc_max_pct=10
dbc_min_pct=5

After this you will notice that **swapper** presence dissapear from top 1st page, then meant that our system handles activation and reactivation of processes when free memory falls bellow minfree, or when the system appears to be **trashing**.

Also you will see the USED line for the device lines from swapinfo -mt > 0. This means no memory pressure and no paging. This will increase performance considerably.

Rgds.