there are some alerts that are automatically hidden (such as when I configure Power mgmt, the previous related alert go away), but not all.

where to find info about their mgmt?

I don't see anything special in "Introduction to Administration Portal"  in RHEV 4.0 docs. Only that it is named "Alerts/Events Pane"....

If I go to the line and right click I have

Dismiss

Delete All

Display All

How do they act exactly?

If I select Display All, I get again what was automatically hidden (eg backup missing alerts and power mgmt conf missing alerts): how to re-hid them (I imagine dismiss, but I would like a global dismiss not one-by-one).

Difference between dismiss and delete?

Thanks in advance 

Gianluca