4 Configuring the Network Environment

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. 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 listen 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 protocol address that specifies the host machine of the listener and a port number.

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

Client Configuration

When a client requests a connection, the listener on the server brokers the request and forwards it to the Oracle database.

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

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

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

You can define your connect descriptors in your tnsnames.ora file on the client machine, located in the ORACLE_HOME/network/admin directory. You can use Oracle Net Manager to configure this file as described in "Configuring Oracle Networking on Client Machines" .

Connection Requests

Users initiate a connection request by providing a connect string. A connect string includes a username and password, and a connect identifier. This connect identifier can be the connect descriptor itself, or a name that resolves to the connect descriptor. One of the most common connect identifiers is a net service name, a simple name for a service. The following example shows a connect string that uses the net service name mydb as the connect identifier.

CONNECT hr/hr@mydb

While the connect identifier shown here is relatively simple, others can be long and inconvenient to use if your environment configuration is more complex. With long connect identifiers, you can map the net service name to the connect descriptor. This mapping information is stored in one or more repositories of information that are accessed with naming methods.

Naming Methods

Oracle Net provides support for the following naming methods:

• Local Naming

• Directory Naming

• Easy Connect Naming

• External Naming

The preconfigured database uses local naming. Only this form of naming is used in this book.

CONNECT username/password@host[:port][/service_name]

CONNECT hr/hr@my-server:1521/mydb

Oracle Net Configuration Assistant

The Oracle Universal Installer launches Oracle Net Configuration Assistant after the database is installed. Use Oracle Net Configuration Assistant to configure the listening protocol address and service information for an Oracle database.

During a typical database install, Oracle Net Configuration Assistant automatically configures a listener called LISTENER that has a TCP/IP listening protocol address for the database. If you do a custom install, Oracle Net Configuration Assistant prompts you to configure a listener name and protocol address of your choice.

Use Oracle Net Configuration Assistant for initial network configuration after database installation. Thereafter, you can use the Oracle Enterprise Manager and Oracle Net Manager to configure and administer your networks.

Enterprise Manager

Enterprise Manager enables you to manage your server-side network configuration with two pages: the Listener page and the Net Services Administration page.

The Listener page displays the listener status and enables you to shut it down. You can navigate to this page from the Home page by clicking the Listener link under General. See "Viewing Listener Configuration" in this chapter.

You can navigate to the Net Services page from the Home page by clicking Listener under General. The Listener page appears. Under Related Links, click Net Services Administration.

The Net Services Administration page enables you to do the following:

• Perform the following administrative tasks for a selected listener:

  • Show current status

  • Change status (start/stop listener)

  • Change tracing settings

  • Change logging settings

• Configure the following:

  • Listener

  • Local naming (tnsnames.ora files) on the machine running the database

  • Directory naming

• Search and sort local and directory naming entries

• Export directory naming entries to tnsnames.ora file

Oracle Net Manager

You can access Oracle Net Manager from the command line or for Windows platforms through the Start menu.

• For command line (UNIX, Linux, or Windows) run netmgr.

• On Windows click the Start button and select Programs, Oracle - oracle_home, Configuration and Migration Tools, and then Net Manager

Oracle Net Manager provides the same features as Oracle Enterprise Manager with the addition of configuring profiles. To learn how to use this tool, see "Configuring Oracle Networking on Client Machines".