One other point I would like to make using sqlplus direct connection is as follows. If you are just planning to use the sql editor to execute the sqcripts or do query form the client manchine and would only be connecting to one perticular instance, then use TWO_TASK. But again you don't have to worry that you wouldn't be able to connect to the other systems, other than TWO_TASK, you can use

sqlplus user_name@service_name

Try to refrain from giving the

sqlplus sys/password@service_name

on Unix systems because, there you would be compromising your password. (i.e, any one who does the ps -ef would be able to see your username and password :confused: )

So one world of advice, don't use

sqlplus sys/password@servicename
or
sqlplus sys/password

Good luck,
Sam