What is ORA-12154: TNS could not resolve service name error in Oracle database

 Would you be interested in knowing what causes ORA-12154 error and how to resolve it? Are you also interested in knowing important tips in order to resolve ORA-12154 error? If so, then you reached the right place. In this article, we will understand how to fix this error. Let's start.

What is ORA-12154 error in Oracle database?

ORA-12154: TNS could not resolve service name is a common error encountered while connecting to an Oracle database. This error occurs when the TNS (Transparent Network Substrate) service is unable to find the service name specified in the connection string.

Here are some tips to resolve the ORA-12154 error:

• Check the TNSNAMES.ORA file: This file is used by TNS to resolve the service name to an actual database connection. Check the file for any spelling or syntax errors in the service name.

• Verify the service name: Make sure that the service name specified in the connection string matches the service name defined in the TNSNAMES.ORA file.

• Update the TNS_ADMIN environment variable: If you are using a different TNSNAMES.ORA file, make sure that the TNS_ADMIN environment variable points to the correct location.

• Check the listener status: Ensure that the listener is running and able to accept incoming connections. You can check the listener status by using the “lsnrctl status” command.

• Restart the listener: If the listener is not running, restart it using the “lsnrctl start” command.

• Check the network connectivity: Verify that the server hosting the database is reachable and there are no network issues preventing the connection.

• Reinstall the Oracle client: If all other steps fail, reinstalling the Oracle client may resolve the ORA-12154 error.

• Verify the Oracle Home environment variable: Make sure that the Oracle Home environment variable is set correctly to the location of the Oracle client software.

• Check the SQLNET.ORA file: This file is used to configure the Oracle Net Services that provide the communication between the client and the server. Verify that the correct settings are configured in the SQLNET.ORA file.

• Use the TNS Ping utility: The TNS Ping utility is used to test the connectivity to the database by checking the availability of the listener. You can use the “tnsping” command to run this utility.

• Check the firewall settings: If the server hosting the database is located behind a firewall, verify that the firewall is configured to allow incoming connections on the specified port.

• Disable the Windows Firewall: If the Windows firewall is enabled, it may be blocking the connection to the database. Try disabling the Windows firewall temporarily to see if it resolves the ORA-12154 error.

• Check the port number: Make sure that the port number specified in the connection string matches the port number used by the listener.

• Try a different connection method: If the error persists, try connecting to the database using a different method such as SQL*Plus or SQL Developer.

• Check for multiple TNSNAMES.ORA files: If you have multiple Oracle client installations on the same machine, there may be multiple TNSNAMES.ORA files. Make sure you are using the correct TNSNAMES.ORA file for your current Oracle client installation.

• Check the service name format: The service name can be specified in different formats such as a simple string, an easy connect string, or a connect descriptor. Make sure that you are using the correct format for your particular scenario.

• Upgrade the Oracle client software: If you are using an outdated version of the Oracle client software, upgrading to the latest version may resolve the ORA-12154 error.

• Check for incorrect hostname or IP address: Verify that the hostname or IP address specified in the connection string is correct and matches the actual hostname or IP address of the database server.

• Verify the SERVICE_NAME parameter in the database: If you are connecting to a database that uses the SERVICE_NAME parameter instead of the SID, make sure that the service name specified in the connection string matches the actual service name in the database.

• Check the network configuration: If you are using a complex network configuration such as a VPN, make sure that the network is configured correctly and that the database server is accessible from the client machine.

• Verify that LDAP is listed as one of the values of the names.directory_path parameter in the sqlnet.ora Oracle Net profile.

Verify that the LDAP directory server is up and that it is accessible.

 

Verify that the net service name or database name used as the connect identifier is configured in the directory.

 

Verify that the default context being used is correct by specifying a fully qualified net service name or a full LDAP DN as the connect identifier

By following these tips, you should be able to resolve the ORA-12154 error and successfully connect to your Oracle database. If the error persists, it is important to seek the help of a qualified Oracle database administrator or support specialist.

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