zipl question

[Betsie Spann]

Hi,
On SuSE, I force a new zipl parm by
/sbin/zipl  -c /etc/zipl.conf

what is the equivalent in RedHat?  The above command doesn't seem to use the 
/etc/zipl.conf file. Where does the boot process get the kernel command line in RH?
Betsie