Stop specific user from log in to application

Requirement:

There are over 300 users in the application. We need to stop the users to log into the application for 3 days every month except for 3 users.

How to add System administrator responsibility from backend

Often oracle apps developers are given only limit access (only certain responsibilities) to the front end application, in such a case you can add a responsibility from back end. We will know how to do this.