From: cross@spitfire.i.gajendra.net

In article <10eaaqr$2sqg0$1@dont-email.me>,
Simon Clubley   wrote:
>On 2025-10-30, Arne Vajhøj  wrote:
>> On 10/30/2025 9:12 AM, Simon Clubley wrote:
>>> On 2025-10-30, gcalliet  wrote:
>>>> It seems now, because the strategy used by VSI or its investor has been
>>>> for ten years a strategy copied on strategies for legacies OS (like
>>>> z/os...), the option of a VMS revival as an alternate OS solution is
>>>> almost dead.
>>>
>>> z/OS is responsible for keeping a good portion of today's world running.
>>> I would hardly call that a legacy OS.
>>
>> z/OS is still used for a lot of very important systems.
>>
>> But it is also an OS that companies are actively
>> moving away from.
>>
>
>Interesting. I can see how some people on the edges might be considering
>such a move, but at the very core of the z/OS world are companies that
>I thought such a move would be absolutely impossible to consider.
>
>What are they moving to, and how are they satisfying the extremely high
>constraints both on software and hardware availability, failure detection,
>and recovery that z/OS and its underlying hardware provides ?
>
>z/OS has a unique set of capabilities when it comes to the absolutely
>critical this _MUST_ continue working or the country/company dies area.

I'm curious: what, in your view, are those capabilities?

>In the VMS world, VMS disaster tolerant clusters were literally a generation
>ahead of what everyone else had as it took 20 years for rivals to be able
>to match the fully shared-everything disaster tolerant functionality that
>VMS has.

I adore the VMS model, but at this point, I think it is fair to
say that it comes from an era where providing those capabilities
at the OS layer was critical.  Now, the OS has effectively
become a commodity (as has the hardware, for that matter) while
those capabilities are provided at the application and
infrastructure layer.  In that world, these things being
integrated at the OS layer matters much less.

I remember when I had the realization, and being somewhat
aghast, when I realized that all of the infrastructure we'd
built out for distributed authentication and authorization was
totally irrelevant to the web applications people were building
on those systems.  Similarly, all of the distributed filesystem
infrastructure and so forth just didn't matter anymore, because
the way people consumed and used data as mediated by a browser
was fundamentally different than the host-based interactive
environment.

>Likewise, to replace z/OS, any replacement hardware and software must also
>have the same unique capabilities that z/OS, and the hardware it runs on,
>has. What is the general ecosystem, at both software and hardware level,
>that these people are moving to ?

I think a bigger issue is lock-in.  We _know_ how to build
performant, reliable, distributed systems.  What we don't seem
able to collectively do is migrate away from 50 years of history
with proprietary technology.  Mainframes work, they're reliable,
and they're low-risk.  It's dealing with the ISAM, CICS, VTAM,
DB2, COBOL extensions, etc, etc, etc, that are slowing migration
off of them because that's migrating to a fundamentally
different model, which is both hard and high-risk.

As for the cloud, the number of organizations moving back
on-prem for very good reasons shouldn't be discounted.

	- Dan C.

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