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Configuring Oracle Network Environment

Oracle Net Listener Configuration

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/12.2.0/dbhome_1, then the listener.ora file is created by default in the /u01/app/oracle/product/12.2.0/dbhome_1/network/admin directory.

The listener is automatically configured when you create a new Oracle database. It just works without any configuration changes.

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))

Service Registration

The oracle database automatically registers with the listener after startip up. Usually it might take a minute or so for the registration to complete.

PMON performs the service registration.

The database can also be manually specified 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.

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

DESCRIPTION=
   (ADDRESS=(PROTOCOL=tcp)(HOST=my-server) PORT=1521))
   (CONNECT_DATA=
      (SERVICE_NAME=mydb.us.example.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. The connect identifier 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:

  1. Easy Naming
  2. Local Naming
  3. Directory Naming

Easy Naming

The easy connect naming method enables clients to connect to an Oracle database by using only a TCP/IP connect string consisting of a host name and service name.

The connection should be in the form [email protected]"host[:port][/service_name][:server][/instance_name]"

The place holders used in the connect identifier format represent:

  • host — the name or IP address of the Oracle database host computer.
  • port (optional) — the TCP port number on which the Oracle Net listener listens for connections.
  • service_name — a database service name.
  • server — the type of service handler. Acceptable values are dedicated, shared, and pooled.

Examples of Easy Naming

[email protected]"dbhost.example.com/orcl.example.com"
[email protected]"192.0.2.1/orcl.example.com"
[email protected]"[2001:0DB8:0:0::200C:417A]/orcl.example.com"

Note

The instance name can be found by using the instance parameter as follows show parameter instance_name.

Note

Oracle database runs on port 1521. If the port is omitted, the clients will connect to port 1521.

Local Naming

Local naming stores the service names in file called tsnames.ora. This file is located in the ORACLE_HOME/network/admin directory. When you create a database using Oracle Database Configuration Assistant (DBCA), local naming is configured automatically.

Directory Naming

Directory naming resolves a database service, net service name, or net service alias to a connect descriptor stored in an LDAP-compliant directory server

Check Listener Status

You can use the lsnrctl command line tool to check the listner status

lsnrctl status

Start the listener

lsnrctl start

Stop the Listener

lsnrctl stop

Connecting to an Oracle Database from a Client Computer

  1. Run the oraenv command line tool to configure the environment variables
  2. Open sqlplus
  3. When prompted, enter the user name followed by an at sign (@) and a connect identifier, where the connect identifier has the following format:

"host[:port][/service_name][:server][/instance_name]"