How to check the current load, logged users on Portal system?

Hi Experts,

We have few clarifications in SAP Portal administration side, Can you please share your views on the following queries.

1. How to check the current load on Portal system or how many users are currently logged in the Portal system and who are they?

2. If we want to shutdown the Portal system is there any automatic option like send a notification mail to all the logged users? If so how to accomplish this?

3. How to ensure that the Portal application server is properly communicating with the Portal DB server? What are the areas/parameters we need to check on the Portal appl server and DB servers--- if the Portal is down due to DB server problem.

Advance Thanks

Regards

Ravi.