This is an optional exercise.

If you have access to an Oracle server, try the following:

1. Display database links: Go to SQL*Plus and enter select * from all_db_links; to see all links you are allowed to use.
   
2. Find your tnsnames.ora file. On UNIX, look in $ORACLE_HOME/network/admin. On a PC, try c:\orant\network\admin.

The results of this exercise will vary and are particular to the server to which you connected and its topology.