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The IBM mainframe: How it runs and why it survives

arstechnica.com

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Re: The IBM mainframe: How it runs and why it survives

#161

Post by graycat »

Ah, good to hear that the IBM mainframes are still around, are more powerful, and that the software for the old IBM mainframes will still run on the new mainframes.

So, yup, JCL still works! An 3270 series video terminals with 24 lines of 80 characters each driven with CICS (customer information control system or some such) is still used.

But I didn't see that

(1) Rexx, often a good replacement for JCL,

(2) XEDIT, and the PC version KEDIT, my favorite text editor,

(3) and VM/370, an impressive virtual machine supervisor, upgraded from the original CP/67 for the IBM 360/67 mainframe

are still supported and used. I would be shocked if they were not still supported and also still used, especially for development and analytical computing tasks.

Re: The IBM mainframe: How it runs and why it survives

#162

Post by sofixa »

lotsoweiners wrote: post #133
sofixa wrote: post #106

Earlier quoted context omitted.

Which part is untrue? That there isn't enough personnel or that it's a severely limiting career choice? Because what you're saying confirms the first one, and for the second one, not a lot of people dream of working on legacy stuff in a big organisation, and those are your only choices if you're a mainframe programmer. Say in the US, for mainframe work, there are what, 30 banks? 5 airlines? 20 insurance companies? No…

Lots of government too. I worked at a government agency that ran it’s business off of mainframe. I worked there as a web developer and we had to consume data from the mainframe in our web apps. Very tedious process.

Yeah, forgot governments, so we can add one more to the list of 'nobody dreams working there as a tech person' list.

Re: The IBM mainframe: How it runs and why it survives

#163

Post by pjmlp »

hinkley wrote: post #125
queuebert wrote: post #108

Earlier quoted context omitted.

I posit that most tech companies make money by poorly recreating old technologies for use by younger people ignorant of the old ones. E.g. how many variants of IRC have we had now? Usenet? VMs?

I think we need history classes in programming, and possibly comparative literature classes but for code.

I had something like that, that is how I upgraded myself from a UNIX zealot into a Xerox PARC one, as I discovered an alternative universe.

Additionaly the campus library was a treasure trove from computing books all the way back in time, and many of us dived into them.

Re: The IBM mainframe: How it runs and why it survives

#164

Post by pjmlp »

jjtheblunt wrote: post #137
hinkley wrote: post #85

Earlier quoted context omitted.

Most of this Cloud technology we like to go all atwitter about is a retread or a redesign of software that's been on mainframes for thirty years. The old farts must laugh themselves silly looking at us acting like we discovered a large white object orbiting the earth.

SUN used to say The Network is the Computer...that always reminds me of what is called "cloud" the last 10+ years.

Basically what cool kids do nowadays with gRPC, I was doing with Sun RPC.

Re: The IBM mainframe: How it runs and why it survives

#165

Post by pjmlp »

Melatonic wrote: post #116
NelsonMinar wrote: post #27

My partner does very technical systems hacking on z/OS. They have a huge problem hiring new programmers. His colleagues are all well over 65 and are inevitably retiring (or worse). It seems like a real problem for the future of the platform.

Lot of people in Taiwan are learning COBOL and mainframe programming specifically for this reason. Surprisingly big (or small, depending on how you look at it) popular of young people learning it.

Big offshoring companies like TCS went big with the Y2K bug correction, and handling COBOL development.

Sometimes that is how one goes big, by taking care of stuff no one is interested into doing, and when there is enough money in the bank, go after everything else.

Re: The IBM mainframe: How it runs and why it survives

#166

Post by ptman »

eeegnu wrote: post #50
kkielhofner wrote: post #19

"They’re designed to process large amounts of critical data while maintaining a 99.999 percent uptime—that’s three seconds of outage per year." Very wrong. Five nines is five minutes and 13 seconds of cumulative downtime in a year[0]. Three seconds of downtime in a year is seven nines[1]. [0] - https://uptime.is/five-nines [1] - https://uptime.is/99.99999

I would guess that they did the calculations, but interpreted it as "5 nines after the decimal point", when it's really "5 nines in total".

0.99999/1 (no %)

Re: The IBM mainframe: How it runs and why it survives

#167

Post by rbanffy »

electroly wrote: post #139
gumby wrote: post #110

Earlier quoted context omitted.

> Going back to the hardware that everyone likes to focus on, it's less radically different from normal servers today than it was historically. The mainframe today is a 19 inch rack like any other. The Main Frame of yore was ... one of the 19 inch racks the computer was made out of (the main one, typically with the ALU and registers in it). And those racks were used because that was how phone systems were built (phon…

The granddaddy of mainframes, System/360, was never in 19" racks. IBM first introduced the use of 19" racks in their midrange lines. What we currently call IBM z didn't adopt standard racks until the 21st century.

I find 19" racks a bit too thin and tall. Definitely their 24" ones were the right proportions.

Re: The IBM mainframe: How it runs and why it survives

#168

Post by rbanffy »

bombcar wrote: post #134
reacharavindh wrote: post #130

Earlier quoted context omitted.

I think its hardware is what enables such reliable software. Hot plug CPUs, memory modules, and DASDs. All survive the failure scenario gracefully. Good luck trying to do that on a rack of x86 servers. I think as in most engineering things. They do a different trade-off and cater to a different niche while x86 servers are the mass market consumables that most workloads -should- be using. The mainframe CPUs go for the…

x86 just made it so the whole computer could drop out of the “cluster” which greatly simplifies the hardware design but the result is NOT a “virtual mainframe” as the software becomes exponentially more complicated if you want “all power”.

It is possible to move that complexity into the platform and outside the applications themselves. When I build a web application I don't need to do anything special about failovers, as long as I remember the local filesystem and state is fungible and it only is persisted when I persist it someplace else (that also employs the same safeguards).

I liked to use Google's App Engine classic environment (the Python 2.7 one) as a good example. It really hammered down some good practices (such as keeping the filesystem read-only) and gracefully handling degraded modes such as a datastore that becomes read-only for no reason or the cache that's supposed to be there that just isn't. It was a great teaching tool.

Re: The IBM mainframe: How it runs and why it survives

#169

Post by rbanffy »

edelsohn wrote: post #86
js8 wrote: post #38

Earlier quoted context omitted.

Since z13 vector instructions are supported again. But I doubt anybody uses them.

The original vector facility is gone, but the Z Vector Extension (VX) is utilized by AI/ML software, such as NumPy, OpenBLAS, etc.

And the bulk of the Telum processor is an inference engine, in essence a very large vector processor (although one tailored for AI inference workloads).

Re: The IBM mainframe: How it runs and why it survives

#170

Post by rbanffy »

bob1029 wrote: post #109
CraigJPerry wrote: post #4

The reason mainframe persists is it's a pretty slick development and deployment environment. A lot things you might cobble together as dependencies - like maybe a database or a message queue, or observability facilities or even deployment strategies like hot-hot deployments - they're all just built in to the platform. That means they're trivial to consume and they're fully supported by one vendor. It's like the world…

I've always looked at IBM like an even more extreme version of Microsoft. I'd probably have us on their path if the cost and knowledge weren't a massive barrier to entry. I know IBM has some cloud thing for us baby startups, but I sure as hell can't figure out how to use it or if our customers are even aware of it. Vertical integration of the business into one magic box is a perpetual dream of mine. Bonus points if I…

I have tried numerous times to get a z/OS LPAR and an AIX VM without any luck. It's a complete mystery to me.
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