Toad for Oracle login screen | TNS Tab | Database name drop-down list box is empty. It cannot find tnsnames.ora file, the DB names or TNS entries are blank.
Create a TNS_ADMIN entry to force Toad to look for the tnsnames.ora file from a specified location:
1. Right-click on the My Computer icon on the Desktop and select Properties.
2. Select the Advanced Tab.
3. Click Environment Variables button.
4. Under "System Variables" | click New | under Variable Name, type: TNS_ADMIN | under Variable Value, type the path to your tnsnames.ora file i.e. C:\oracle\product\10.2.0\client_1\NETWORK\ADMIN\ | click OK.
5. Start Toad and re-test the issue.
