I'm new using Oracle, and I need to stablish a connection to ORACLE to diferent databases.

1- To do it, the connection string uses the user name, password and Server. A server could have different databases or represents only one?. If it has different databases explain me how to specify one to make a query.

2- Which OWNER y have to use to acces only data of the database tables, columns and foreing keys references to avoid obtaining system tables in my querys.

P.D: If you see I'm realy lost, explain me the two concepts.

Thank you,
Rodrigo

You need the username, password, hostname, port and SID. TNSNAMES lets you define a label for the hostname, port and SID combination, so for example you might use scott/tiger@work where "work" is defined in tnsnames.ora as host=starbase, port=1521, SID=dev.

That is just the old TNS though. There is also Oracle Names, Oracle Instant Client, ODBC and about 94 flavours of JDBC so far as I can make out.