Here we will see how to connect Oracle database from UNIX (Linux or Solaris) shell.
If you are using oracle10g then copy and paste below lines in your bash shell.
export ORACLE_SID=SNM
export ORACLE_HOME=/opt/app/oracle/product/10.2.0
/opt/app/oracle/product/10.2.0/bin/sqlplus username/password@customer_dbname
Or
Step1: Switch user as oracle user
su – oracle
Step2: Connect database using username
connect username@database
If you want to connect to privileged default user then enter
CONNECT / AS SYSDBA
If you want to connect current node as a privileged user.
CONNECT username AS SYSDBA
Username – current node user