The IBM mainframe: How it runs and why it survives • Hacker News Board

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

#181

Post by tracker1 » Tue, Jul 25, 2023, 3:41 PM UTC

ibiza wrote: post #32

mberning wrote: post #8

Earlier quoted context omitted.

It persists in many places due to the deeply ingrained belief that, for one reason or another, it would be technically, practically, or economically impossible to migrate functionality off the mainframe. Somehow the people in charge of these systems have managed to convince large enterprises of this for decades . And now we are in a situation where their long held beliefs have become true because nobody is around tha…

Migrating a suite of programs written w/ COBOL, CICS, DB2 from z/OS to Linux is fairly straightforward. MicroFocus COBOL compiles IBM COBOL, DB2 runs on Linux or you can swap out another RDBMS. The CICS part requires a simple runtime easily implemented in C plus a new scanner to replace the calls in your programs. I was part of a 4 person team that knocked this out in under a year. 1,000's of mainframe programs runni…

Worth noting, in the 90's general computing was still increasing at a very rapid pace, where you could replace a late 80's mainframe with an early 90's x86 or PPC server. You won't have the built in layers of redundancy, but that isn't always necessary for any given environment. The cases of many mainframes still in use today are on much faster/newer systems where that critical uptime is much more important.

I'm not really a fan of mainframes, only pointing out that the companies still on them are generally on them as a direct replacement to general purpose servers isn't purpose fit, and conversion is excessively costly, even compared to IBM mainframe contracts.

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

#182

Post by tracker1 » Tue, Jul 25, 2023, 3:46 PM UTC

TheRealDunkirk wrote: post #121

ghaff wrote: post #13

Earlier quoted context omitted.

It's what would be cool and would look good on my resume. (Only half /s)

Over my 30 years, mostly in Fortune 250's, I've seen 3 mainframe migrations fail. If you're part of the team, the trick is to get another job before people realize -- in year 4 of your "5-year" migration -- that it was never going to work, because managers in other parts of the business will never allow their headcount to be reduced by better IT workflows.

Having worked adjacent to some of these kinds of projects, can't upvote this enough. Not to mention that business doesn't take the suggested 1-2 years to simply document and define test cases for the old/new system to ensure such a new system works, and simply start working on the new system based on what the business/da types drew up. Missing literally tens of thousands of legal edge cases defined in the legacy codebase.

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

#183

Post by tracker1 » Tue, Jul 25, 2023, 3:48 PM UTC

sofixa wrote: post #162

lotsoweiners wrote: post #133

Earlier quoted context omitted.

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.

Yeah, the hiring process is often 6+ months long for half the pay of private sector jobs, and 1/5 the pay of the consulting companies they bring in to do the bulk of the work anyway.

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

#184

Post by reacharavindh » Tue, Jul 25, 2023, 5:03 PM UTC

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”.

In a way, yes, swapping out entire computers are how one is expected to work with x86 machines. Ask anybody running a critical state full workload(Relational database with lots of writes for example) and they will tell you how nice it is to have a system so reliable to run their writes onto.

Running a Postgres cluster or a Kafka cluster on a bunch of x86 machines sure gives you scale, but definitely brings the pain of handling availability scenarios for write consistency. Distributed locks and distributed data stores that use Raft/Paxos serve as a good reminder of how hard it is to achieve them. If IBM could do it at hardware level, some Enterprise customers are willing to loosen their rich wallets for that comfort.

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

#185

Post by rbanffy » Tue, Jul 25, 2023, 5:38 PM UTC

neverartful wrote: post #172

rbanffy wrote: post #170

Earlier quoted context omitted.

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.

IBM probably doesn't make mainframe LPARs available over the internet because the cost of the LPAR would be cost prohibitive to any potential customer. On the other hand, a z/VM guest or an LPAR on POWER should absolutely be an option.

They do. A z/OS with a single CPU and 4GB of RAM costs around $2000/month. It's a bit of a hassle, as you need to connect to its VPN and will need to add a public network gateway for your machine to see the world, but that's it. It could, of course, be just a tiny slice of z/OS running under a larger LPAR, but IIRC, LPARs can get really small. You can go as far as 16 vCPUs and 128GB of RAM for roughly $30K/month.

Last time I tried I had issues with the VPN and couldn't connect to it. I'll try again later. Another good thing about IBM cloud is that they embrace Terraform and you can download templates for just about everything they offer.

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

#186

Post by jjtheblunt » Tue, Jul 25, 2023, 6:07 PM UTC

pjmlp wrote: post #164

jjtheblunt wrote: post #137

Earlier quoted context omitted.

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.

no kidding. same here.

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

#187

Post by hinkley » Tue, Jul 25, 2023, 6:48 PM UTC

pjmlp wrote: post #163

hinkley wrote: post #125

Earlier quoted context omitted.

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.

The distributed computing class had a history of distributed computing component.

But it was an elective, and as I found once I got into the real world, one that most people either opted out of or didn't have the option to take. I spend way too much time providing Cliff's Notes to a class I took almost thirty years ago.

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

#188

Post by hinkley » Tue, Jul 25, 2023, 6:54 PM UTC

wkat4242 wrote: post #153

jjtheblunt wrote: post #137

Earlier quoted context omitted.

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

Sun was way ahead of its time. Too far ahead in fact, in the sense that they brought products to market that the market didn't yet realize they wanted. The Javastation network computer for example, it was a bit like a Chromebook (though incredibly slow -lol)

I think Sun should probably have bought Azul systems during the tech downturn. Even if it turned into a reverse merger (which history suggests may have been the case), it might still be around today.

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

#189

Post by skywal_l » Tue, Jul 25, 2023, 8:14 PM UTC

hinkley wrote: post #85

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…

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.

All this is true but you forget the cost. Mainframe do not allow to start small. I have no idea how much the cheapest mainframe cost but it's porbably more than a dirt cheap x86 server with a bunch of free software so important for student projects, training, hobbies, start-up and cost constrained industries.

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

#190

Post by hermitdev » Tue, Jul 25, 2023, 8:56 PM UTC

rvba wrote: post #140

hermitdev wrote: post #68

Earlier quoted context omitted.

> DB2 runs on Linux The DBA's I interned with would yell at you for this claim. They'd say UDB runs on Linux, but DB2 only runs on z/OS. I worked with both DB2 & UDB during my internship 2 decades ago, and while largely compatible with core SQL functionality, that changed quickly after you got off the "normal" path. UDB was released at a much faster cadence, and if you developed to the latest features of UDB, you'd o…

What company had 10k developers on a mainframe?

It'd probably be more accurate to say users than developers on the LPAR. I won't name names, though. It was at a Fortune 500, though. Manufacturing sector, not finance.