oracle set up monitoring

Oracle database is one of the largest relational database management systems in the world and is widely used in enterprises and organizations. When using Oracle, setting up a listener is one of the very important steps that can help you control the connection between the application and the database. This article will introduce how to set up the Oracle listener.

1. What is an Oracle listener?

The Oracle listener is a separate process that receives connection requests from client and server processes and passes them to the appropriate database instance. Through listeners, clients can interact with the database.

2. Set up the listener

In this section, we will discuss the steps on how to set up the listener. The following are detailed steps:

1. Check whether the listener is running. The required listeners are usually automatically created during the Oracle installation. On a Linux system, you can check if the listener is running using the following command:

$ ps -ef | grep tnslsnr

If the listener is running, you can see the running tnslsnr process. If it is not running, you need to start it manually before you start using the database.

2. Query the listener version. You can use the following command to query the listener version:

$ lsnrctl version

This command will return version information.

3. Edit the listener configuration file. By default, the listener configuration file is named listener.ora. You can find it in the $ORACLE_HOME/network/admin directory. To edit the file you can use the following command:

$ vi $ORACLE_HOME/network/admin/listener.ora

In this file you need to add an entry to specify the listener to listen on protocol, port and binding information. Here are some example configurations:

SID_LIST_LISTENER =
(SID_LIST =

(SID_DESC =
  (SID_NAME = PLSExtProc)
  (ORACLE_HOME = /u01/app/oracle/product/12.1.0/dbhome_1)
  (PROGRAM = extproc)
)
(SID_DESC =
  (GLOBAL_DBNAME = orcl)
  (ORACLE_HOME = /u01/app/oracle/product/12.1.0/dbhome_1)
  (SID_NAME = orcl)
)

)

LISTENER =
(DESCRIPTION_LIST =

(DESCRIPTION =
  (ADDRESS = (PROTOCOL = TCP)(HOST = example.com)(PORT = 1521))
)

)

In this configuration, SID_LIST_LISTENER contains a list describing all database instances to be listened to. This list must contain a SID_DESC entry for each instance to be listened to.

At the end of the list, there is a separate entry describing the network protocol and port information to be used by the listener.

4. Check the listener configuration file. Once you have finished editing, you can check that the syntax of the listener configuration file is correct using the following command:

$ lsnrctl status

If your configuration file contains any errors, this command will throw An error occurred.

5. Restart the listener. When you edit a listener configuration file, you need to restart the listener for the changes to take effect. You can restart the listener using the following command:

$ lsnrctl stop
$ lsnrctl start

6. Test the listener. To test whether the listener is working properly, you can use the following command:

$ tnsping example.com

If the listener is running, this command will return an "OK" message.

7. Enable and disable listeners. Sometimes, you may need to disable or enable a listener in a specific scenario. You can use the following command to disable the listener:

$ lsnrctl disable

You can use the following command to enable the listener:

$ lsnrctl enable

3. Summary

In the Oracle database, the listener is a very important and necessary component. Listeners, if set up correctly, can help you have better control over database access and connections. In this article, we introduced how to set up a listener and discussed some related parameters and settings. If you set up your listeners correctly, you will be able to achieve better database performance and reliability.

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