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Lesson 8 Overview of Oracle's topology solution, part 2
Objective Describe the role of database links in establishing database connectivity.

Take Service Name, Add remote user ID, password

Role of Database Links in establishing Database Connectivity

Having defined a service name, the next step in establishing database connectivity is to create database links that take the service name and add a remote user ID and password. Once defined by the DBA, these remote databases can participate in queries and updates from within any Oracle application. For example, databases in London and Paris can be defined to the Denver system with the following SQL extension:

CREATE PUBLIC DATABASE LINK london
 CONNECT TO 'user_id' IDENTIFIED BY 'secret_password'
 USING 'london_unix';
CREATE PUBLIC DATABASE LINK paris
 CONNECT TO 'user_id' IDENTIFIED BY 'secret_password'
  USING 'paris_vms';

The USING clause

The optional USING clause supplies the connect string that the database link is to use:
USING 'prodsales'
Although this clause is optional, you must supply it unless there is already a public database link to the destination database using the desired connect string.

How Database Links Are Resolved