ORA-12154 ERROR !!!

This error message occurs when a user attempts to logon to an Oracle database. The tnsnames.ora file was not found or has a syntax error. The Oracle communications software (SQL*Net) did not recognize the database connect descriptor as being valid. For GUI utilities, this is the name entered in the third field of the ORACLE logon box.

ORA-12154 TNS:Could not resolve service name

Cause: The service name specified is not defined in the TNSNAMES.ORA file.

Action: Make the following checks and correct the error:
- Verify that a TNSNAMES.ORA file exists and is in the proper
place and accessible. See the operating system specific manual
for details on the required name and location.
- Check to see that the service name exists in one of the
TNSNAMES.ORA files and add it if necessary.
- Make sure there are no syntax errors anywhere in the file.
Particularly look for unmatched parentheses or stray characters.
Any error in a TNSNAMES.ORA file makes it unusable. If possible
regenerate the configuration files using the Oracle Network
Manager.