Hi,
In Oracle there is a global database name that uniquely identifies a database in the network.The global database name is in the format
database_name.domain_name

e.g. test.world where test=database and world is the domain name

The default domain name in Oracle is world.In case u want it to have other domain name change the init.ora file and make domain_name= and bounce back the database.Also make change in ur tnsnames.ora file to reflect the new change.

In case of any probs please be free to write to me at [email protected]

regards,
Rohit nirkhe,Oracle DBA,OCP 8i