I want to change some kernel parameters in HP-UX11, to do with Oracle upgrade/install.

I know this is done using SAM. I am told SAM will not let you enter values outside the allowable range. Could anyone tell me if they have experienced anything different?

In Solaris, I would copy the /etc/system file elsewhere and if a boot was to fail I would just point it at the copied system file.

Sounds strange. My experience is that sam has never refused my input yet.
Which parameter are you talking about and what is the output of uname -a?

It is true that sam will validate changes to the kernel and reject illegal input. You don't need to use sam, but then the procedure varies from release to release and we do not know what release is involved here. With recent releases, the command kmtune would be used to adjust a value and kmtune also validates input.

I think malcqv is trying to understand how to recover is the new kernel does not work. That almost never happens anymore since kernel changes are vetted at input time. But you would interrupt the boot sequence and boot the previous kernel which is usually in /stand/vmunix.prev for recent releases.