Role of ORACLE_SID?

Hi!
I've been debugging a log on problem for the last few days and I think I'm in the process of finding the error in my idea of how the oracle connection is established.
So, can anybody explain to me the role of the environment variable ORACLE_SID in a scenario where the client sits on a different machine from the db server?

I had assumed, when I set ORACLE_SID to the Db SID then sqlplus would, when called "sqlplus name/passwd" check the environment for the SID, consult tnsnames on where to find a db with that sid and then connect to it.

Is this wrong?
From my experiments it seems to be that I *always* have to call sqlplus like "sqlplus name/passwd_at_networkDbName". Is this correct?

Lots of greetings!
Volker
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While it is a known fact that programmers never make mistakes, it is still a good idea to humor the users by checking for errors at critical points in your program.
-Robert D. Schneider, "Optimizing INFORMIX  Applications" Received on Thu May 22 2003 - 09:17:45 CDT