Distributed Oracle databases are built on database links. In a nutshell, a database link is a connection from one database to another that is available to users having proper privileges any time both databases are available. The purpose of database links is to make remote data available for queries and, in some cases, updates. Because a database link is essentially a stored login to a remote database, the DBA must take care to ensure that it does not compromise the security of either the local or the remote database. This section discusses database link naming conventions, the different types of database links, different methods of creating them, restrictions, security concerns, and how to report on them.
If the GLOBAL_NAMES INIT.ORA parameter is set to its default value of FALSE, you can use any name you want for a database link. I worked at one site where one developer was partial to the name “Fred” for the links he created. Informality may be acceptable in a small organization, but not where more than three or four databases are in use.
The most intuitive approach is to use the naming convention DB_NAME .DB_DOMAIN for all database links, for example, D7CA.BIGWHEEL.COM. Setting GLOBAL_NAMES to TRUE enforces this convention of database links having the same name as the database to which they connect. If you are using advanced replication, you must set this parameter to TRUE.
Note that you can change the global name of any database instance ...