That looks a lot like a similar problem in another instance of trying to get graphics applications to work when switching user from the login user. I refer specifically to this: a logged in user wants to su to root, then run an application that requires graphics. The same error messages are the result. The cure: the normal user issues the command 'xhost +localhost', then su to root, and start the app from the command line. The root user can then have a GUI app running.
So, my suggestion to you is to try that. Before logging in as oracle user, issue the command 'xhost +localhost', then login as oracle.
It's worth a try. If it fails, you haven't lost anything.