I have a database \"TEST\", to which I connect at address 123.45.67.89:1521.
How do I connect to it using PL/SQL Developer?
I am facing to this problem so many times till I have 32bit PL/SQL Developer and 64bit Oracle DB or Oracle Client.
The solution is:
Edit or create a TNSNAMES.ORA file in c:\app\admin\product\11.2.0\client_1\NETWORK\admin folder like mentioned above.
Try with TNSPING in console like
C:>tnsping ORCL
If still have problem, set the TNS_ADMIN Enviroment properties value pointing to the folder where the TNSNAMES.ORA located, like: c:\app\admin\product\11.2.0\client_1\network\admin