>sqlplus /nolog              Just startup SQL*PLUS but haven't connected to DB

>sqlplus / as sysdba      Use os authentication

>sqlplus user/pwd         Use db authentication

SQL>startup                  Startup Oracle service (should startup TNSListener at first)

SQL>shutdown

SQL>connect user/pwd                        Local connection

SQL>connect user/pwd@host:1521    Remote connection *1* *2* *3*

SQL>connect system/pwd                   The pwd is the SYSTEM password that you set upon installation of Oracle Database XE.

>lsnrctl status               View listener status

>lsnrctl start

>lsnrctl stop

>lsnrctl reload

>lsnrctl services

>emctl start dbconsole  

>emctl start agent       start up the EM Grid Control facility

>isqlplusctl start         start up the iSQL*Plus server

Note
*1* Logging in to the Oracle Database XE host computer with an ssh (or telnet ) session and then starting SQL Command Line (or other Oracle command-line utility) is considered a local connection, even though you start the ssh (or telnet ) application on a remote computer.

*2* The remote computer must have Oracle client software installed.

*3* Only Oracle Database XE Client supports the notion of a default database service. If you connect remotely from any Oracle client software other than Oracle Database XE Client, you must include the XE service name.