kernal parameter need to be tune

[Viney Kumar]

Hi all

i need to tune the some kernal perameter on HP-UX 11.11
dbc_max_pct
dbc_min_pct
maxswapchunks

pls share steps for it and wht step we need to take percautionaly

thanks

[Mel Burslan]

your best bet is to use sam. Go to kernel parameters and drivers menu item from the main menu and the selection should be self explanatory.

Make sure you understand, after you make these kernel changes, your system will reboot. If this is a production server, you might want to check with people if a reboot is accaptable before you commit to it.

[Steven E. Protter]

Shalom,

The first two parameters are the high and low figures fore the buffer cache. The last controls how much swap your system can use.

All three are not listed as dynamic kernel parameters and therefore require a compile of the kernel and reboot.

kmtune -l

# lists them.

kmtume also permits you to set up changes.

You can also use sam kernel menu to set up and guide you through changes.

If this is oracle, the buffer cache being high does not benefit you at all. I generally set these to 5 and 7 on an oracle server, and have recently played with the concept of setting them the same.

It is very expensive in terms of system CPU time for the system to change the buffer cache. Its better to set it and forget it unless your system will benefit from a different figure, which should be a conscious decision of a systems administrator.

SEP

[Sharma Sanjeev]

Hi Vinay

Please use SAM if you are not familier with Command line.SAM will recompile Kernal & as these are static pearemeters so requires reboot

Regards
Sanjeev

[Ganesan R]

Hi,

I would also recommand to use SAM to change these kernel parameters. If you still need the commands to do it, follow these steps.

# cd /stand/build
# /usr/lbin/sysadm/system_prep -s system
# kmtune -s dbc_max_pct=value -S system
# kmtune -s dbc_min_pct=value -S system
# kmtune -s maxswapchunks=value -S system
# mk_kernel -s system
# mv /stand/system /stand/system.prev
# mv /stand/build/system /stand/system
# kmupdate
# shutdown -ry 0

[Vishu]

I also recommend going through SAM, if not familiar with the command-line.

If not, then Ganesan has pasted the exact procedure to follow.

[Mel Burslan]

additional comment to my previous posting:

I you are asking how to change a kernel parameter, I'd strongly suggest you DO NOT use the command line method. sam provides additional error checking, protecting you against trivial errors like a mistyped or forgotten character etc.