Try this

path....
date....
.....
mksysb -i -e -X -p /dev/rmt0 >> /tmp/mksysb.log 2>&1
if [ $? -eq 0 ]

        echo "$CMD:\t$DATE $TIME - MksysB completed successfully" >>
/tmp/services.log
        date >> /tmp/mksysb.log
else
        echo "$CMD:\t$DATE $TIME - MksysB failed" >> /tmp/services.log
fi
tctl -f /dev/rmt0 rewoffl

Jeroen