Understanding Network Configuration

Oracle Net Listener Configuration

On the database server, the Oracle Net listener, commonly known as the listener, is a process that listens for client connection requests. It receives incoming client connection requests and manages the traffic of these requests to the database server.

The default listener configuration file is called listener.ora, and it is located in the Oracle_home/network/admin directory. The file contains a protocol address that identifies the database. This address defines the protocol the listener is listening on and any other protocol-specific information. For example, the listener could be configured to listen at the following protocol address:

(DESCRIPTION=
   (ADDRESS=(PROTOCOL=tcp)(HOST=my-server) (PORT=1521)))

This example shows a TCP/IP address that specifies the host computer of the listener and a port number.

The listener.ora file is automatically configured during installation, but can be reconfigured with Oracle Enterprise Manager Database Control. For more information, see "Viewing Listener Configuration" and "Starting and Stopping the Listener" .

Because all of the configuration parameters have default values, it is possible to start and use a listener without configuring it. This default listener has a name of LISTENER, supports no service names upon startup, and listens on the following TCP/IP protocol address:

(ADDRESS=(PROTOCOL=tcp)(HOST=host_name)(PORT=1521))

An Oracle database registers with the listener within a minute or so of starting up. Supported service names, that is, the service names, or databases, to which the listener forwards client requests, can be configured in the listener.ora file, or this information can be dynamically registered with the listener. This dynamic registration feature is called service registration. The registration is performed by the process monitor (PMON) process—an instance background process—of each database instance that has the necessary configuration in the database initialization parameter file. Dynamic service registration does not require any configuration in the listener.ora file.

Connect Descriptors

The client uses a connect descriptor to specify the database to which it wants to connect. This connect descriptor contains a protocol and a database service name. A database can have multiple service names defined, so a specific service name must be specified for the connect descriptor. In a preconfigured database, there is only one service name, which defaults to the global database name.

The following example shows a connect descriptor that enables clients to connect to a database with service name mydb.us.acme.com:

(DESCRIPTION=
   (ADDRESS=(PROTOCOL=tcp)(HOST=my-server) PORT=1521))
   (CONNECT_DATA=
      (SERVICE_NAME=mydb.us.acme.com)))

Connection Requests

Users initiate a connection request by providing a connect string. A connect string includes a user name and password, and a connect identifier. This connect identifier can be the connect descriptor itself, or a name that resolves to the connect descriptor using mapping information stored in one or more repositories accessed with the naming methods described in "Naming Methods". This name is referred to as a net service name.

Naming Methods

A naming method is a resolution method used by a client application to resolve a connect identifier to a connect descriptor when attempting to connect to a database service.

Oracle Net provides support for the following naming methods:

• Easy Connect Naming

• Local Naming

• Directory Naming

Tools for Network Configuration

Oracle Database enables you to manage your network configuration with the following tools:

• Net Configuration Assistant

• Oracle Enterprise Manager

• Oracle Net Manager