Connecting to database from remote client

• Start listener on server machine
• Install adminstrative client s/w on the client machine and add server name in tnsname.ora in client machine
•  Verify on client machine:
• tnsping <servicename>
• sqlplus tpcc/tpcc@bench (where tpcc is the username and bench is the service name)
• setenv TWO_TASK bench
• sqlplus tpcc/tpcc (you should get the prompt)
•  
• What is the use of TWO_TASK environment variable ?

If you are in a Unix environment, you can normally set 2 environment variables:
ORACLE_HOME 
ORACLE_SID 

that will connect you to a local database identified by that home and sid. If you wanted 
to be able to connect to a remote database or a database on that machine via SQLNet, you 
can also set:
 TWO_TASK = <tnsconnect string> 
The setting of TWO_TASK overrides the ORACLE_SID when set. You will not connecting to a 
local database with two_task but rather using sqlnet to connect to a remote database.
So, instead of: 
$ sqlplus scott/tiger@some_db 
I can: 
$ setenv TWO_TASK some_db
$ sqlplus scott/tiger
and the @some_db is implied.