How to force session timeout on BI iViews?

Hello,

I have an iView which presents a certain query from our backend BI.

I tried an experiment: I ran a report and left it on my screen for greater at least 60 minutes. I then went back in and ran the report again.

As far as I know the portal timeout session is 20 minutes but in that case I was able to run the report again and wasn't re-prompted to input my passwords or log on again.

I would like not to allow users to be able to use the portal at all after an idle time of 20 minutes, not even if they triger a BI report from an iView which just uses as a window to the BI.

How can I accomplish that?