The Oracle Transparent Network Substrate (TNS) facilitates simple inter-database communication.
To implement TNS, Oracle has built a management layer over the standard network topology.

To implement Net8, several Oracle files must be present on the server:

1. tnsnames.ora defines outgoing database requests. It contains all database names (SIDs) running on the processor.
   When a new database is added to a box, the file /etc/tnsnames.ora must be updated.
   This file also describes each domain name, including protocol, host, and port information.
   
2. istener.ora contains a list of destinations for incoming database connections.. When a new destination database is added to a box, it must be added to /etc/listener.ora and the listener must be bounced.

In addition, TNS uses several server files to resolve host and service names. On UNIX, these files include:

1. /etc/HOSTS lists all the host names and their corresponding IP addresses.
   
2. /etc/SERVICES lists the SQL*Net services and their IP addresses.

The following SlideShow illustrates how a connection is made.
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