ora-12154:TNS :could not resolve the connect identifier spec

Dear Sir

My oracle version is 9.2.0.1.0 and I have installed DB Tool for oracle software into my local machine.I am getting the below error while trying to connect through DB Tool

	Code:
	ora-12154:TNS :could not resolve the connect identifier specified

But when I am connecting through PL/SQL Developer I am able to conect the user as well as the password.There is no problem comming in the connecting the user through Pl/SqL Developer.
The issue is coming in the client machine.Let me also tell you that the server is located at different location.
Can you please help me as to how to resolve the above issue.I checked TNSNames.ora the connection is succesful.and I am able to connect through PL/SQL DEveloper.

How I should connect the user through DB Tools for Oracle

You have an issue with your Oracle configuration. Perhaps you have multiple Oracle homes and different tools/programs are using different homes. That's why you can connect from some programs but not from other.
Make DB Tools use the same Oracle home that you use with PL/SQL. On the Connect dialog, there is a little yellow folder button that you can to pick a particular Oracle home directory.

By the way, database journey dedicated entire article to ORA-12115 and how to correct it. You can see it here http://www.databasejournal.com/features/oracle/article.php/3092461