agree those particular technologies are not now mainframe exculsive - however mainframe grade systems allow switching / reconfiguring all components on line. E.

agree those particular technologies are not now mainframe exculsive - however mainframe grade systems allow switching / reconfiguring all components on line. E.g. plug in a new processor unit (e.g one of N processor racks plugged into the system bus), new IO unit, new disk unit, replicate all data, move all jobs, decouple the old one so that after the operation is complete 0% of the old hardware is running and 100% new, with no downtime.