How to set shared memory kernel params.

I need to change some of the shared memory kernel parameters on my Solaris 8 sparc box. I thought that all I had to do was set them in the /etc/system file, then reboot. The syntax I am using in that file is like:

set SEMMNS=256

This does not seem to change anything though. I issue a sysdef command and nothing has changed, even after a reboot. I need to change these in order to have Oracle 9i install correctly. Oracle tells me what the minumum parameters must be, but not how to change them.

Thanks for the help.