Oracle 11g Networking Concepts

1. Database Instance Names
      As you know by now, an Oracle instance consists of the SGA and a set of Oracle processes. The database instance name is specified in the initialization file (init.ora) as the INSTANCE_NAME parameter. When you talk about the Oracle system identifier (SID), you are simply referring to the Oracle instance.
2. Global Database Names
     The global database name uniquely identifies an Oracle database and is of the format database_name.database_domain, for example, sales.us.acme.com. In this global database name, “sales” is the database name and “us.acme.com” is the database domain.
     Since no two databases in the same domain could have the same database name, every global database name is unique.
3. Database Service Names
     A service can cover more than one database instance.  You can identify each database in your system by its service name, and you specify the service name of a database with the SERVICE_NAEM  Initialization parameter.
     The parameter’s value defaults to the global database name.
4. Connect Descriptors
     To connect to any database service in the world from your desktop, you need to provide two bits of
   information:
           •   Name of the database service
           •   Location of the address
   Oracle uses the term connect descriptor to refer to the combined specification of the two necessary components for a database connection: a database service name and its address. A connect descriptor address portion contains three components: the communications protocol used for the connection, the host name, and the port number.

RIA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 172.20.0.88)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SID = RIA.Microsoft.com)
    )
  )

Then we can connect  oracle database:
x:\> SQLPLUS CONN system/manager@RIA

We can use the both  Net Configuration Assistant and Net Manager tools to configure the ..\NETWORK\ADMIN\tnsnames.ora file.