The ORA-12154: TNS:could not resolve the connect identifier specified error occurs when a client is trying to connect to an Oracle database and the client is unable to resolve the service name specified in the connect descriptor.
There are several possible causes for this error:
The TNSNAMES.ORA file on the client machine is not configured correctly. The TNSNAMES.ORA file is used by the Oracle client to resolve service names to connect descriptors. Make sure that the TNSNAMES.ORA file is configured correctly and contains the service names and connect descriptors for the databases you are trying to connect to.
The LISTENER.ORA file on the server machine is not configured correctly. The LISTENER.ORA file is used by the Oracle listener to resolve service names to connect descriptors. Make sure that the LISTENER.ORA file is configured correctly and contains the service names and connect descriptors for the databases you are trying to connect to.
The SQLNET.ORA file on the client machine is not configured correctly. The SQLNET.ORA file is used by the Oracle client to configure various networking options. Make sure that the SQLNET.ORA file is configured correctly and contains the correct settings for your network.
There is a problem with the network connectivity between the client and the server. Make sure that the client and server are able to communicate with each other over the network.
To troubleshoot this error, you can check the following:
Check the TNSNAMES.ORA file on the client machine and make sure that it is configured correctly and contains the correct service names and connect descriptors.
Check the LISTENER.ORA file on the server machine and make sure that it is configured correctly and contains the correct service names and connect descriptors.
Check the SQLNET.ORA file on the client machine and make sure that it is configured correctly and contains the correct settings for your network.
Check the network connectivity between the client and the server. Make sure that the client and server are able to communicate with each other over the network.
If you are still unable to resolve the error, you may need to contact Oracle support for further assistance.