Oracle Net Listener Configuration

On the database host, the Oracle Net listener (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 network/admin subdirectory of the Oracle home directory. For example, if your Oracle home directory is /u01/app/oracle/product/11.2.0/dbhome_1, then the listener.ora file is created by default in the /u01/app/oracle/product/11.2.0/dbhome_1/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=dbhost.example.com) (PORT=1521)))

This example shows a TCP/IP protocol address that specifies the host computer of the listener and a port number. The listener can listen for connection requests on network interfaces with either IP version 4 (IPv4) or IP version 6 (IPv6) addresses.

The listener.ora file is automatically configured during installation.

Because the configuration parameters have default values, you can start and use a listener without configuring it. This default listener is named LISTENER, supports no service names on 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. The service names, or the databases that they represent, to which the listener forwards client requests, can be configured in the listener.ora file. This information can also be dynamically registered with the listener. Dynamic registration of services and databases with the listener is called service registration.

Service registration is performed by the listener registration (LREG) process—an instance background process—of each database instance. Dynamic service registration does not require modification of the listener.ora file.