If a MIGRATION will cause violation of must rule then that migration will be cancelled by DRS.

IF DPM is trying to put a HOST in sleep MODE for power saving but migration of VM’s running on this host can cause a must rule violation, it will prevent DPM to put that host in sleep mode.

If HA is trying to restart VM’s after a host failure but if restart of some VM’s on a particular host can cause must rule violation then HA will either restart those VM’s on some different host or COULD not restart them at all if no suitable host is available for failover.

If a migration will cause violation of must rule then that migration will be cancelled by DRS.

IF DPM is trying to put a host in sleep mode for power saving but migration of VM’s running on this host can cause a must rule violation, it will prevent DPM to put that host in sleep mode.

If HA is trying to restart VM’s after a host failure but if restart of some VM’s on a particular host can cause must rule violation then HA will either restart those VM’s on some different host or could not restart them at all if no suitable host is available for failover.