Sorry its not very clear for me

But to make my point clear...

CREATE DATABASE LINK ABC.XYZ.COM CONNECT TO ABC IDENTIFIED BY XYZ USING 'ABC.XYZ.COM';

Even this works try out in your instance, but Database link tries to connect once you give the request to access information from remote.

Try to connect from your Oracle Server to Remote Server using sqlplus or others.

If it fails then you need to have tnsnames entry in your server.