Whereas on mainframe the service processors can deal with it transparently to the CPU using specialized hardware.
And let's say it's financial transactions - fixed-point decimal arithmetic. On mainframe, that can be hardware accelerated too.
That said, it is not at all clear to me that the TCO of a maxed-out IBM DS8900F is less than $30 million/year.
Yeah no. I worked on mainframe code for 15 years of the last 20 and can tell you that you’re wrong. Even reasonably simple business lines have cobbled together insane cobol, batch and cics screens that would make spaghetti blush.
When you open up a 100,000 line batch program that’s just 1 of 30 cobol programs in that run which is a mess of gotos, global mutable state and basically every single other generally frowned upon software practice we know about, you start to understand the issues.
Moving off of mainframe is practically impossible because of it. That other person being voted down is actually correct, nobody in the organization actually knows how any of it works.
When organizations try to transition away, what ends up happening is they get these insane promises of “5 years” from vendors (like IBM. Ask me how I know!), but then it takes 10 years to transition single systems.
Nothing is documented. So you have business people who have no clue how anything works providing high level work flows. But then there’s always 50 random edge cases or interactions they never considered cause the 40 year old code just does it.
IT contains most of the business knowledge, but the mainframe grey beards are… stubborn. The business hangs on to these people because they’re seen as insanely valuable, not realizing that the grey beards have actually been actively suppressing knowledge to only their hidden documents, and they’ve got 8 years till retirement and are going to make sure that their job exists at least until then by actively sabotaging efforts to change. But also, for some reason, the business manager love the saboteurs. It’s insane to watch.
how do you know?
Because they keep the shit running. If you're a bank and responsible for trillions of dollars in assets and billions of dollars in daily transactions, the absolutely last thing you can afford is downtime or, even worse, data loss. You'll not just have to handle a ton of angry customers, but in the worst case attract regulatory attraction or getting dragged in front of Congress and the courts.
Here in Germany, Deutsche Bank is integrating 12 million accounts from Postbank to their own IT systems, and it has been an utter utter shitshow [1], attracting a lot of bad press and the banking regulator BaFin is also investigating [2].
[1] https://www.merkur.de/leben/geduldsprobe-fuer-postbank-kunde...
[2] https://www.sueddeutsche.de/wirtschaft/deutsche-bank-postban...
> It is never technical or pratical reasons, always economic reasons. To use contemporary vocabulary, you "just" need to replicate a "multi tenant HA cloud environment" to migrate from a mainframe at great cost.
When your business processes are so ossified by a mainframe that you have, say, groups preparing Excel spreadsheets -- with data formatted from one mainframe screen in 3 columns -- for use by another group to input back into the mainframe -- with the data reformatted in 4 columns -- you know you're never escaping the gravity well of the black hole at the center of IT that is "The Mainframe." This is just how it's going to be until the company is so technically irrelevant that the remains are picked up in a fire sale by some PE to sell off to some other, tangentially-related company, solely for the IP assets.
It is never technical or pratical reasons, always economic reasons. To use contemporary vocabulary, you "just" need to replicate a "multi tenant HA cloud environment" to migrate from a mainframe at great cost.
> And now we are in a situation where their long held beliefs have become true because nobody is around that understands how or why the software works the way it does.
Statistically unlikely, most of the business software that goes onto said mainframe is in fact very simple and straightforward and can be easly ported out, however, the real deal is all the integration and high availability logic built-in into "the mainframe platform". You're not porting that out without replicating said "multi tenant HA cloud environment" at great cost.