[ovirt-users] how does host's status changes ? Especially Unassigned or NonOperational or NonResponsible

Hi all, I'm confusing in Host's status in Ovirt Eninge. When will the host's status become Unassigned or NonOperational or NonResponsible? and If the host's status change to these statuses, What will ovirt response to it? After reading Ovirt Engine's source code, I find Only HostMonitoring.java and AutoRecoveryManager.java will change the status of Host. for example, If the host's status is changed to NonOperational, The AutoRecoveryManager will traverse the NonOperational hosts and calling ActivateVdsCommand.java, which will only set the Host's status to Unassigned ? But I don't know What's the next step? So where I can find the article or manual or other helpful information about this question? Thank you . Your sincerely Mark