You will see more detailed
examples of distributed database management in Chapter 17.
Each object in a database is uniquely identified by its owner and name. For example, there
will only be one table named EMPLOYEE owned by the user HR; there cannot be two tables of
the same name and type within the same schema.
Within distributed databases, two additional layers of object identification must be added.
First, the name of the instance that accesses the database must be identified. Next, the name of
the server on which that instance resides must be identified. Putting together these four parts of
the object??™s name??”its server, its instance, its owner, and its name??”results in a global object
name. In order to access a remote table, you must know the table??™s global object name. DBAs and
application administrators can set up access paths to automate the selection of all four parts of the
global object name. In the following sections, you will see how to set up the access paths used by
Oracle Net.
The foundation of Oracle Net is the Transparent Network Substrate (TNS), which resolves
all server-level connectivity issues. Oracle Net relies on configuration files on the client and the
server to manage the database connectivity. If the client and server use different communications
protocols, the Oracle Connection Manager (described in a later section of this chapter) manages
the connections. The combination of the Oracle Connection Manager and the TNS allows Oracle
Net connections to be made independent of the operating system and communications protocol
run by each server.
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