In order for the Oracle server to start automatically at system boot time, create the file /etc/init.d/oracle like this:

#!/bin/bash
#
# Run-level Startup script for the Oracle Instance and Listener
#
# chkconfig: 345 91 19
# description: Startup/Shutdown Oracle listener and instance

ORA_HOME="/u01/app/oracle/product/9.2.0.1.0"
ORA_OWNR="oracle"

# if the executables do not exist -- display error

if [ ! -f $ORA_HOME/bin/dbstart -o ! -d $ORA_HOME ]
then
        echo "Oracle startup: cannot start"
        exit 1
fi

# depending on parameter -- startup, shutdown, restart 
# of the instance and listener or usage display 

case "$1" in
    start)
        # Oracle listener and instance startup
        echo -n "Starting Oracle: "
        su - $ORA_OWNR -c "$ORA_HOME/bin/lsnrctl start"
        su - $ORA_OWNR -c $ORA_HOME/bin/dbstart
        touch /var/lock/subsys/oracle
        echo "OK"
        ;;
    stop)
 	# Oracle listener and instance shutdown
        echo -n "Shutdown Oracle: "
        su - $ORA_OWNR -c "$ORA_HOME/bin/lsnrctl stop"
        su - $ORA_OWNR -c $ORA_HOME/bin/dbshut
        rm -f /var/lock/subsys/oracle
        echo "OK"
        ;;
    reload|restart)
        $0 stop
        $0 start
        ;;
    *)
        echo "Usage: $0 start|stop|restart|reload"
        exit 1
esac
exit 0

Now run chkconfig oracle for updating the run level information.

Try service oracle start|stop|restart to check that everything works as expected now.

If you reached this step without errors: congratulations. Else, check Section 9, “Miscellaneous Errors” for troubleshooting suggestions.