Instructions on how to use a single TNSNAMES.ora file for Oracle tools given that multiple tnsnames file can exist and be difficult to maintain.
Step 1- Create a folder on your workstation or shared drive location for your team. Step 2- Copy a tnsnames.ora file to that location. Step 3- Modify the tnsnames.ora file as needed. Step 4- On each respective workstation that you wish to configure to using the tnsnames.ora file ‌ Open Control Panel and access the System Properties icon. Then select Environment Variables on the Advanced tab. Step 5- Add a new User Variable called TNS_ADMIN and set the value to the path to your newly created folder. Do not include the filename, just the path. Click OK/Apply to save all changes. It should not be necessary to reboot, but you will need to exit your Oracle tools at the very minimum. From this point forward you simply maintain the one copy of the tnsnames.ora file.