Does anyone know what kinds of companies or applications make use of z/OS mainframes?
There is a z/OS security talk I saw that partially dispels the myths and prejudices against mainframes as legacy. In some cases z/OS is more modern than what you might find on your desktop and OSs like Linux are implementing features in its kernel that have been in zOS for years.
I also wanted to mention that where I've worked and many other places there is a crisis of brain drain at companies as the mainframe experts who are highly paid retire out and there are programs to recruit young people who are more attracted to other platforms. There is a lot of pay and job security in the field. I know of one situation where a guy past retirement is paid full salary to work 1/3 of full-time from his vacation home because the company could not afford to lose his knowledge and struggled to find someone competent enough to learn under him that was interested in mainframe. In other words, someone young with these skills would be highly paid and in higher demand at many companies.
http://www-03.ibm.com/systems/z/education/academic/masterthe... and https://www.facebook.com/MasterTheMainframe
I get the feeling it's mostly legacy plus scenarios where the rigor IBM applies is valuable and you go along with whatever they suggest.
What makes them "faster" in many cases is that the decades old apps were written by people "with a clue" and they run pretty much on the hardware. I've had a joke going for a few years, that websphere was created to cause efforts to port off the mainframe to fail.
AKA its pretty much impossible to take something running in ztpf, rewrite it in java and plunk it on a EC2 instance and have a hopes chance in hell of making it work without spending more than the next two decades of mainframe maintenance costs in monthly amazon bills.
That doesn't mean you can't rewrite it in C++ on a DL580 with an attached Flash840 and leave the mainframe in the dust if you have competent programmers.
The zSeries selling point is not the hardware, but the reliability (which is in fact the hardware). The z in that series stands for zero down time and they are not selling hardware, but close to 100% reliability.
Now in reality, no one can guarantee zero down time, but IBM does in fact guarantee 5 nines (99.999%) and 6 nines (99.9999%) up time and that guarantee costs money.
You certainly can't get those sort of up-time numbers using nothing but commodity hardware.
Another way to view this: since mainframe workloads have existed for a long time, if their performance was way beyond what you can still accomplish with commodity hardware, then we should see tech companies utterly flocking to these systems. We should see IBM selling their chips all over (after all, why wouldn't Microsoft want to get in on the action?). No one wants to deal with huge fleets of servers. If they could just give IBM some money and be done, they'd do that, no?
But instead it's mostly used for older, risk adverse, applications. So while I've no doubt they end up delivering solid systems, I'm skeptical that the scale is more massive than people are used to.
I've seen some retailers in the North East try and "get off the mainframe" by moving to a modern ERP from Oracle or SAP only to have the projects fail after spending $250m-$500m and to this day they are still running 20-40 year old backend software for things like financials, pricing, payroll and merchandising. I've seen production COBOL code running that was authored in the late 70's.
However, they do use newer technologies on GUI's etc that integrate with their mainframe solutions. People often have to keep working with two, inconsistent systems at once, though.
There are a few exceptions obviously. Microsoft, Apple, HP, etc. are unlikely to use IBM technologies internally. Facebook, Amazon, etc. are young enough to not have mainframes.
You can go search for z/OS job openings and see everyone from Walmart to Lockheed Martin to Citibank.
But, yeah, they don't use it any more. Most mainframe users are legacy users. However, there's occasional conversions especially for consolidation. IBM's competitor, Group Bull, posted some case studies on that such as consolidating hundreds of desktops and servers onto 2 easily-managed mainframes with cost savings.
But the result actually meant Microsoft had to then eat their own dog food and in a strange way it forced Microsoft to greatly improve their server platforms to where they are today.
So in a funny way it probably backfired on those early Microsoft detractors.
Cornell University also used to run HR and accounting on a 370 mainframe and people were happy, but then they switched to peoplesoft and now (i) they are not happy, and (ii) looking for a new accounting system.
There are still places using non-IBM mainframes as well. Several state welfare systems use Unisys mainframes.
For many big name banks and credit cards, it's pretty safe to assume that a Z/OS mainframe is doing some work with the data you've generated with every swipe.