VMS and MVS did a lot of stuff quite differently tho'. I'd say VMS kinda straddled what MVS and VM did; VM was much more pleasant to use than MVS for interactive computing (I mean CMS compared to TSO... bleh; though ISPF certainly has its fans) but I'd much rather use VMS than either. MVS probably did huge amounts of batch better and I guess they were much of a muchness with TPS and DB, though VMS had the advantage of clustering.
Looking back, one of the interesting things is that the S/3x0 adherents always point out the huge number of IO channels and multiple paths but during the same time period DEC (and ICL, for that matter) were moving to NAS with what's essentially RAID 0+1 in common parlance. I'm not sure IBM had anything like that at the time.
I would say that there would be zero chance of VMS ever running on an S/3x0 given that architecturally, the IBM CPUs were so very different to Vax processors, though I am reminded of some stuff I read about the Jupiter project where the KC10 was intended to have sufficiently flexible reprogrammable microcode that it could be in essence a 36-bit Vax if that's what you wanted it to be. plus the intention of the KC10's IOPs to handle bus-and-tag natively since so many PDP-10 shops ran IBM-compatible storage connected to their 10s with converter boxes. I'm not sure if any of that was in any sort of development or just a wish list, tho'; And I'm not sure if IBM ever intended its 3x0/z-series to be anything other than what they are.
Biting the hand that feeds IT
