descusion - kernel configuration parameter

[Fadia Almarei]

Dear All
i have a descusion question, the kernel configuration parameter is a system parameter that affect the system maily,changing these parameter to an undesired value may corrupt the system,but is changing these parameter will affect the application found in this system,and if it does ,i think when i return the parameter to it's original value this application must run ,as the system is OK.
your feedback please
BR,
Fadia

[Geoff Wild]

That is correct.

Changing the kernel must not be taken lightly.

Good docs here:

http://docs.hp.com/en/5990-8172/ch03s09.html

http://docs.hp.com/en/TKP-90202/ch01s02.html

Rgds...Geoff

[Tor-Arne Nostdal]

1) Some kernel values is dynamically changeable. These can be set online and you dont have to create a new kernel.
You can use the command kmtune to query the values and see if a parameter is dynamically changeable.

2) If you permanently change a kernel value, the new value is "compiled" into the kernel. Parameters that is not dynamically changeable must be activated after a kernel recreation and a boot.
You can either create a kernel from command line or by SAM.

If problems:
Under normal circumstances you should keep a copy of the old kernel (default name /stand/vmunix.prev) and the old kernel parameter file (/stand/system.prev)

If you have problems with the new kernel, you can interrupt the automatic boot sequence and then boot from the old kernel.

If you have been configuring kernel both with SAM and from command line, you might have used different kernel parameter files during kernel creation.
You could then have trouble when reverting to previous config...

example scenario:
- Old kernel generated by SAM
using kernel "parameter file A"
Running application OK

- Generating new kernel from command line
using kernel "parameter file B"
Running application FAIL

If you then try to just set the parameter back in "parameter file B" - you might still have problems if the application needs some paramters from "parameter file A".