Originally posted by yanban
If you want to connect without a listener (assuming you are where the Db resides), the oracle_sid entrie in the registry must be set to the instance you want to connect to.
Nonsence. What if you have more than one instance under the same oracle_home? Would you manualy edit registry each time you want to connect to a particular instancve without the listener?

Simply set the ORACLE_SID env variable whichever way you want it (command line, user environment) and you'll have no problem connecting to your database without the listener, even if you don't have ORACLE_SID entry in your registry at all.