As the OMS owner (e.g. 'oms')...
mkdir /u01/tmp
cp $ORACLE_HOME/sysman/install/EMDeinstall.pl /u01/tmp
$ORACLE_HOME is assumed to be set in the .profile of the 'oms' user.$ORACLE_HOME/perl/bin/perl /u01/tmp/EMDeinstall.pl -mwHome $ORACLE_HOME -stageLoc /u01/tmp
Manually remove the auto start scripts from /etc/rc.d
rm /etc/rc.d/*/S98*gcstartup
rm /etc/rc.d/init.d/gcstartup
rm /etc/rc.d/init.d/lockgcstartup
rm /etc/rc.d/init.d/unlockgcstartup
Example output
Note that there are some "interesting" errors here but deinstall is still reported as successful.