I was interviewed by tcs and they put this question on me like this:
i)In your organization, there are 100 developers out of which lets say 5 are not able to connect to the oracle.

ii) Lets say that they are able to connect with 2 different session but are not able to connect one more session. As a DBA how you are going to look at this issue and what will be your action plan.

from where you find the problem and how you resolve it.