Extreme security measures on database objects are mitigated by lax
security on referenced operating system files.
Database Links and Remote Databases
Database links allow an Oracle database to reference objects stored outside of the local database.
The command create database link creates the path to a remote database, which in turn allows
access to objects in the remote database. A database link wraps together the name of the remote
database, a method for connecting to the remote database, and a username/password
combination to authenticate the connection to the remote database. In some ways, a database
link is similar to a database synonym: A database link can be public or private, and it provides
a convenient shorthand way to access another set of resources. The main difference is that the
resource is outside of the database instead of in the same database, and therefore requires more
information to resolve the reference. The other difference is that a synonym is a reference to a
specific object, whereas a database link is a defined path used to access any number of objects
in a remote database.
For links to work between databases in a distributed environment, the global database name
of each database in the domain must be different. Therefore, it is important to assign the initialization
parameters DB_NAME and DB_DOMAIN correctly.
To make using database links even easier, you can assign a synonym to a database link to
make the table access even more transparent; the user does not know if the synonym accesses an
object locally or on a distributed database.
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