Oracle databases - startup and shutdown

Shutdown:

$ export ORACLE_SID=db_sid
$ sqlplus /nolog
sql> connect / as sysdba
sql> shutdown immediate

Startup :

$ export ORACLE_SID=db_sid
$ sqlplus /nolog
sql> connect / as sysdba
sql> startup mount
sql> alter database open;

Note: This needs to be done by logging on the machine where oracle database is installed