2nd instance of oracle on same machine

Hello,

	We have Oracle installed on a partition (on a 1Gi drive) with 
	enough space on the partition to install another instance of
	Oracle.  I was looking through the RDBMS manual on how to do
	this on the same machine, but only describes the method for
	different machines.  I was told that one can install another
	instance of Oracle on the same machine, but is rather difficult
	partly because there is only one orasrv process defined in the
	/etc/services file.  We are running SunOS on a Sparc10.  My
	project manager said that there are no other machines available
	to install Oracle on, due to disk space.  Could someone explain
	to me how I would go about installing another instance of Oracle
	on the same machine (on the same partition)?  Any help is 
	appreciated!

				-- John