Oracle Listener |VERIFIED| Download

Note that all connections established before the listener stopped will be unaffected. Because stopping the listener prevents the incoming connections, it does not disconnect those that are already connected.

Another way to execute the listener command is through the command line without going into the listener control interface. For example, to view the status of the listener, you can use the following command in the command line on Windows or Terminal on Linux:

Oracle Listener Download

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Oracle Net Listener is a separate process that runs on the database server. It receives incoming client connection requests and manages the traffic of these requests to the database server. Find out how to configure the listener to accept client connections.

A listener is configured with one or more listening protocol addresses, information about supported services, and parameters that control its runtime behavior. The listener configuration is stored in a configuration file named listener.ora.

Because the configuration parameters have default values, it is possible to start and use a listener with no configuration. This default listener has a name of LISTENER, supports no services on startup, and listens on the following TCP/IP protocol address:

The listener forwards client requests to supported services. These services are dynamically registered with the listener. This dynamic registration feature is called service registration. The registration is performed by the Listener Registration (LREG) process. Dynamic service registration does not require any manual configuration in the listener.ora file.

Service registration enables the listener to forward client connect requests to the least-loaded instance and dispatcher or dedicated server. Service registration balances the load across the service handlers and nodes.

Service registration allows processes, such as an Oracle database, to identify their available services to the listener, which then acts as a port mapper for those services. The listener uses the dynamic service information about the database and instance received through service registration.

Dynamic service registration is configured in the database initialization file. It does not require any configuration in the listener.ora file. However, listener configuration must be set to listen on the ports named in the database initialization file, and must not have parameters set that prevent automatic registration, such as COST parameters.

By default, the LREG process registers service information with its local listener on the default local address of TCP/IP, port 1521. If the listener configuration is synchronized with the database configuration, then LREG can register service information with a nondefault local listener or a remote listener on another node. Synchronization occurs when the protocol address of the listener is specified in the listener.ora file and the location of the listener is specified in the initialization parameter file.

For a shared server environment, you can use the LISTENER attribute of the DISPATCHERS parameter in the initialization parameter file to register the dispatchers with a nondefault local listener. Because the LOCAL_LISTENER parameter and the LISTENER attribute enable LREG to register dispatcher information with the listener, it is not necessary to specify both the parameter and the attribute if the listener values are the same.

A remote listener is a listener residing on one computer that redirects connections to a database instance on another computer. Remote listeners are typically used in an Oracle Real Application Clusters (Oracle RAC) environment. You can configure registration to remote listeners, such as with Oracle RAC, for dedicated or shared server environments.

In a dedicated server environment, you must enable the LREG background process to register with a remote listener. You do this by configuring the REMOTE_LISTENER parameter, which is a comma-delimited list parameter, in the initialization parameter file. The syntax of REMOTE_LISTENER is as follows:

In the preceding command, listener_address is resolved to the listener protocol addresses through a naming method such as a tnsnames.ora file on the database host. If a comma appears in the listener address, then the entire string must be enclosed in quotation marks.

In a shared server environment, you can use the same registration technique as for a dedicated server environment. Alternatively, you can set the LISTENER attribute of the DISPATCHERS parameter in the initialization parameter file to register the dispatchers with any listener. The syntax of the LISTENER attribute is as follows:

The LISTENER attribute overrides the REMOTE_LISTENER initialization parameter. Because the REMOTE_LISTENER initialization parameter and the LISTENER attribute enable LREG to register dispatcher information with the listener, you do not need specify both the parameter and the attribute if the listener values are the same.

For example, assume that a remote listener named listener-sales2 listens on port 1521 on host sales2-server, and a database resides on host sales1-server. You want the listener on sales2-server to redirect connection requests to this database. Figure 9-1 illustrates this scenario.

A network may contain multiple local and remote listeners. By default, all listeners are cross-registered with each other. By specifying a set of listeners in the LISTENER_NETWORKS initialization parameter, you can designate a subset of local listeners with a subset of remote listeners. Listeners specified by the LISTENER_NETWORKS parameter should not be specified by the LOCAL_LISTENER and REMOTE_LISTENER parameters.

Assume there are two distinct networks, network1 and network2. On network1, there is a local listener named local1, and a remote listener named remote1. On network2, there is a local listener named local2, and a remote listener named remote2. The following syntax sets up registration so that the listeners only redirect connections to listeners on the same network.

In the preceding example, local1 is registered only with remote1, and remote1 only redirects connections to local1. The listener local2 is registered only with remote2, and remote2 only redirects connections to local2.

On the database to which you want requests to be redirected, set the REMOTE_LISTENER parameter in the database initialization parameter file to the alias of the remote listeners, and the LOCAL_LISTENER parameter to the alias of the local listener.

The listener name alias specified for the LOCAL_LISTENER or REMOTE_LISTENER initialization parameters, or LISTENER attribute can be resolved using a tnsnames.ora file. For example, a listener can be defined in the init.ora file as the following:

The CONNECT_DATA information should not be included in the network service entry in the tnsnames.ora file. However, Oracle Enterprise Manager Cloud Control and Oracle Net Manager cannot configure a tnsnames.ora file without the CONNECT_DATA information. To use listener name aliases, Oracle recommends you modify the tnsnames.ora file using a text editor.

During an Enterprise Edition or Standard Edition installation on the database server, Oracle Net Configuration Assistant automatically configures a listener with a name of LISTENER that has a TCP/IP listening protocol address for Oracle Database. During a Custom installation, Oracle Net Configuration Assistant prompts for the listener name and protocol address.

A listening IPC protocol address for external procedure calls is automatically configured, regardless of the installation type. Oracle Net Configuration Assistant also automatically configures service information for the external procedures in the listener.ora file.

For TCP/IP, if the computer has more than one IP address and you want the listener to listen on all available IP addresses, then select TCP/IP or TCP/IP with TLS and enter the host name of the computer in the Host field.

When configuring the listener to listen on TCP/IP, enter the default port of 1521. Otherwise, you must configure the LOCAL_LISTENER parameter in the initialization parameter file and the non-default port number must be specified for use by any naming method.

By default, Oracle Net Listener permits only local administration for security reasons. As a policy, the listener can be administered only by the user who started it. This is enforced through local operating system authentication.

Oracle recommends that you perform listener administration in the default mode (secure by means of local operating system authentication), and access the system remotely using a remote login. Oracle Enterprise Manager Cloud Control can also be used for remote administration.

Connections coming to listener on an IP (TCP, TCPS, and SDP) based endpoint with firewall functionality enabled, go through service ACL validation. The listener after receiving the service name validates the connection IP with ACL list.

Listener registration should be restricted to valid nodes and subnets. Valid nodes and subnets can be specified for registration, and excluded nodes can also be specified for registration. By default, every incoming connection for registration at the listener is subjected to IP-based filtering. A connection is only allowed if it originates from the local machine. If the other nodes and subnets are specified for registration, then the local machine and the ones specified are allowed. The following parameters can be set in the listener.ora file to specify valid and restricted nodes and subnets:

REGISTRATION_INVITED_NODES_listener_name: Specifies the nodes that can register with the listener. The list can be host names, or CIDR notation for IPv4 and IPv6 addresses. Presence of a host name in the list results in all IP addresses mapped to it being invited.

By default, the SCAN listener agent sets REMOTE_ADDRESS_REGISTRATION_listener_name to a private IP endpoint. The SCAN listener accepts registration requests only from the private network. Remote nodes that are not accessible to the private network of the SCAN listener must be included in the list of valid nodes by using the registration_invited_nodes_alias parameter in the listener.ora file, or by modifying the SCAN listener using the command-line interface, SRVCTL. e24fc04721