The steps of start|stop db server as follows:
1.start lisening
$lsnrctl start | stop
2.start or stop datebase
$sqlplus /nolog
sql>connect /as sysdba
sql>startup | shutdown immediate
3.start or stop dbconsole
$emctl start | stop dbconsole
4.start or stop iSQL*Plus
$isqlplusctl start | stop

]]>