SCAN host

http://www.symantec.com/business/support/index?pag...

Hi Friends,

I have some querries regarding SCAN host.I have read the manuals and the above link.But i have some doubts.

1. Scan host can change if it is down?
2. Scan host and drive owner for Shared drive are same?
3. Scan host is permanent for a drive throughout?
4. Role of SCAN host?