> To be honest while I think for CMS, VM is the ¡°bees knees¡±, when you try to run MVS in a VM the wheels can fall off the car
> because of the need to maintain shadow page tables.
I run MVS as a guest of VM.? In fact that is the only way I run it.? It runs great, and I am not sure why there is so much misinformation about the 'negative aspects' of running this way.? To be sure, if I had 30 other CMS users online on the same system competing with MVS and a few batch jobs and some TSO users, then there would definitely be some serious issues.? But we're all basically single users on our systems.? We have no one else to compete with and even if there were one or two others it would be negligible.
For me at least, the advantages of having CMS and TSO side by side are worth some reduction in MVS throughput.? Ok, so my 2000 line batch assembly takes 8 seconds instead of 6.? I can wait.? I can submit jobs from CMS to MVS; they come in through MVS's card reader, and I can get my job output spooled back to my CMS virtual reader when the job is completed.? Or I can use TSO all the way for the same process.
I do run MVS in a 8 MB virtual machine.? I have CP generated for an 8 MB V=R area.? This allows me to run STBYPASS (Shadow Table Bypass) and avoid that overhead.? This support is present in Sixpack 1.3 (I know, I installed it there for you, Dave).? And as a V=R guest, CCW translation can be turned off for MVS, thereby saving another good bit of overhead.? Many of the new ECPS:VM assists that I introduced in 2017 and 2018 (in Hyperion and SDL Hyperion only) were geared to specifically assist guests like MVS.? ECPS:VM now works with STBYPASS and it now assists several expensive instructions like LRA, STOSM, and more, that MVS issues in abundance.? And even if you can't run STBYPASS (because you don't have Sixpack 1.3 or are running MVS V=V), the newer ECPS:VM support also assists shadow and page table validations.
Let's don't complain about it!? Let's get out there and try it.? I think you'll be pleasantly surprised.
Regards,
Bob
