oracle cannot start monitoring

When using Oracle database, you may encounter a situation where monitoring cannot be started. This is very inconvenient for users who want to connect to the Oracle database because they cannot access the database and perform the required operations. At this point, we need to solve this problem so that the monitoring can work properly.

There may be many reasons why monitoring cannot be started. Generally speaking, there are the following situations:

1. Listener configuration error: There may be errors or incorrect configuration in the monitoring configuration file. Correct, so the listener cannot be started.
2. Port conflict: There may already be a process listening on the same port, which will cause Oracle monitoring to fail to start.
3. Network connection problem: There may be problems with the network connection, such as network instability, firewall settings blocking the connection, incorrect network address, etc., which may result in the inability to connect to the monitor.

In response to the above problems, some solutions are provided below.

1. Listener configuration error

If you find an error in the listener configuration file, you can try to re-edit the configuration file to ensure that it conforms to the correct format and content. Generally speaking, under Linux or Unix operating systems, the listener configuration file is located in the $ORACLE_HOME/network/admin directory, while under Windows operating systems, the file is located in the %ORACLE_HOME%
etwork dmin directory. Edit configuration files can be opened using a text editor, such as Notepad.

In the configuration file, we need to set the listener name, protocol, port number and other information. If we do not select a custom path from the Oracle installer, Oracle automatically sets the installation path to $ORACLE_HOME. Therefore, we can find the listener configuration file listener.ora in the above path.

If you have checked the file for correctness and the problem persists, you can try using Oracle Net Configuration Assistant to recreate the listener. This tool allows users to create listeners and service names through a GUI interface to ensure the correctness of the listeners.

2. Port conflict

When encountering a port conflict, you need to use the port tool to check whether a process is already using the port, and to determine which application or service is listening to the port. port. You can use the netstat or lsof command to check the status of a network port and which application is using it. If a port conflict occurs, you can try changing the port number. The port number and other parameters can be changed in the listener configuration file to ensure that the listener does not occupy a port that is already occupied.

3. Network connection issues

If a client connected to the Oracle database cannot connect to the listener, it may be due to a network problem. You can check whether the network connection is working properly and ensure that important information such as IP address, port, listener and Oracle database are correct. If the remote host is disabled by the firewall, firewall rules need to be enabled.

In addition, it is recommended to configure the local listening address in the listener configuration file of the Oracle database. The local listening address can be localhost or 127.0.0.1. It is usually located on the last line of the listener configuration file.

Finally, if you cannot start the listener, you can try restarting the Oracle database service and then restart the listener. If the problem persists, consider upgrading to the latest version or looking for other possible solutions online.

In short, the inability to start the listener is very troublesome for users using Oracle databases. If you encounter such a problem, don't panic and follow the suggestions above to troubleshoot and resolve it. This ensures that your Oracle database is working properly and meeting your needs.

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