The following error appeared when you are trying to conenct to database using toad applicaion: –
Make sure of the following :-
- Database is up and running
- Listener is up and database is registered using.
if the above steps is done and still facing the same issue then do the following :-
- Right Click on my computer and choose properties.
- Advance system settings.
- Environment Variable.
check the below entry is exsits, if not add it by press on new and follow the same steps by adding TNS_ADMIN and the location of the tnsnames.ora, sqlnet.ora into the 2nd box like the picture below.