ORA-12154: TNS: Could not resolve the connect identifier specified

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The ORA-12154 error typically occurs when Oracle cannot resolve the connect identifier specified in your connection string. Here are some steps to troubleshoot and resolve this issue to connect session smoothly.

Check the tnsnames.ora File:

Ensure that the tnsnames.ora file exists in the $ORACLE_HOME/network/admin directory.

Verify that the file contains the correct service name and connection details. The format should look something like as below.

<Address_Name> =

  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(Host = <hostname>)(Port = <port>))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = <service_name>)
    )
  )

To check connection description is valid or not.

$tnsping (DESCRIPTION =(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(Host = )(Port = ))) (CONNECT_DATA =(SERVICE_NAME = )))

If your connection description is correct, it will ping successfully.

Check Environment Variables:

Ensure that the ORACLE_HOME and TNS_ADMIN environment variables are set correctly in context file.

These variables should point to the correct Oracle installation and network configuration directories.

Verify Connection String:

Double-check the connection string in your PLSQL Developer to ensure there are no typos.

Sometimes enclosing the connection identifier in quotation marks can resolve the issue.

Permissions:

Ensure that the tnsnames.ora file has the appropriate read permissions for the user or process trying to access it.

Network Issues:

Verify that there are no network issues preventing access to the database server.

Ensure that the hostname and port specified in the tnsnames.ora file are correct and reachable.

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