
ABCs of IBM z/OS System Programming Volume 1 - emersonrsantos
http://www.redbooks.ibm.com/Redbooks.nsf/RedbookAbstracts/sg246981.html?Open
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DigitalJack
If your software stack has per core licensing, a z/architecture mainframe can
make a lot of sense. They are extremely efficient at running virtual machines
(with linux guests for example). Where an Intel cluster can handle 10-20 VMs
per core, a z/arch mainframe can do 100s per core.

They have dedicated processors for offloading IO operations, which has a big
impact on reducing pipeline stalls, and also part of why they are so much
better at handling a multitude of VMs.

They have 4 levels of cache, with gigabytes of memory at level 4, data is kept
close to the processors.

The hardware costs a lot, but if your software is licensed per core, there is
a good chance you could save millions compared to an Intel solution. It
depends on your usage scenario though. If everything is open source and you
aren't paying per core fees, then there is probably no advantage for you.

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Spooky23
_cough_ Oracle _cough_

Just be careful with this strategy. When you could start offloading per-socket
IBM licensed software to more performant multi-core Intel or POWER CPUs, IBM
switched from socket to "Processor Value Units". (Aka "give us more money")

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savramescu
A single core is not equivalent to a hexa core so I think PVU's make more
sense in today's world. What I would like from them is to be more transparent
with the requirement to use ILMT.

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morenoh149
Does anyone know what kinds of companies or applications make use of z/OS
mainframes?

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surge
Every large financial institution, airline, or large company that does
millions of transactions an hour that isn't competing with IBM or young enough
to implement a different platform that can scale to that level.

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.

~~~
ghuntley
That would be Soldier of Fortran -
[https://www.youtube.com/watch?v=Xfl4spvM5DI](https://www.youtube.com/watch?v=Xfl4spvM5DI)

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surge
Right I love his stuff. I was thinking of his talk at BSides LV 2014 which he
gave the same talk but he also had talks this year also at BSides and DefCon.

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.

~~~
DigitalJack
Is there any way to learn this sort of thing outside of being at a company
with a z/architecture mainframe? I know about the Hercules project, but as far
as I can tell, you can only run predecessors to Z/OS (due to licensing as I
understand it), and zLinux.

~~~
ghuntley
Yep. IBM has been running a hackathon since early 2002 all around the world as
a recruiting funnel to resolve the talent shortage problems @surge refers to.
Runs every year, all across the world and there are always great prizes
(mainframe tshirts, ipads, iphones, macbook pros) just for completing the
exercises plus side-track options to drop out of uni and instantly obtain six-
figure employment at one of IBM's customers if you do well.

[http://www-03.ibm.com/systems/z/education/academic/masterthe...](http://www-03.ibm.com/systems/z/education/academic/masterthemainframe/)
and
[https://www.facebook.com/MasterTheMainframe](https://www.facebook.com/MasterTheMainframe)

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renownedmedia
"... a 13-volume collection that provides an introduction ..."

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wyclif
What's the z/OS jobs scene like now?

~~~
nickpsecurity
Best time to get in it. Learn mainframe, CICS, RPG, and COBOL. Among these are
many jobs that work steady hours with pay that stays the same or increases
over time due to lack of labor. Boring, predictable work. Pretty much the
opposite of IT in general. And remember that you can always do consulting or
FOSS in modern tech after hours for fun. ;)

~~~
marktangotango
What do you base this on? There are also tens of thousands of layed cobol
programmers who are unemployed or working in other fields (in the US), the
legacy of offshoring and cost reduction of the past 15 years.

I am one. I started mainframe cobol in 2003, grew the skills you listed for 5
years. It's a miserable existence for anyone really interested in
developement. The company I worked for had just started their off shoring
program when I switched to JEE (I took a pay cut, but am way ahead now). That
same company subsequently laid off most of their onshore developers.

This is mainframe applications programming today, there maybe jobs, but not in
the US.

~~~
nickpsecurity
There's job adds all over the country plus people retiring. Personally, I
think it varies area by area. Places with a lot of big companies with legacy
systems need employees. Others... not so much.

The offshoring issue is real. It's why most of America's brightest in CompSci
and Math are going to financial sector instead of IT. Any time I meet someone
trying to get into IT I recommend against it. Only exception, which is risky,
is embedded where the need to physically be there reduces offshoring risk.
ASIC's, too, so long as you get out of RTL work as quickly as possible: it's
all going to Asia.

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joshbaptiste
Airline GDS such a Sabre are on such systems.

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MyDogHasFleas
AFAIK, SABRE is/was an airlines reservation system, not a GDS. SABRE evolved
into TPF which is not related to z/OS except inasmuch as they are both
operating systems that run on IBM z-series mainframes.

See [http://www-03.ibm.com/systems/z/os/](http://www-03.ibm.com/systems/z/os/)
for a list of IBM z-series operating systems.

~~~
bdg
I worked with SABRE -- it's a GDS, and a reason I really want to avoid the
entire industry.

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nickpsecurity
Looks like an uphill, learning experience.

~~~
StillBored
And frustrating for anyone with extensive experience with modern software
stacks. The zseries is a strange combination of semi-modern hardware with
ancient software/hardware practices. I spent a year of my life with a recent
mainframe as part of my previous job. During that time I discovered a long
list of things that are frankly unbelievable to anyone familiar with modern
computing. I should write a book about all the crazy crap, but I don't really
have too. Just reading the install/setup/operating guides with a mainframe in
hand should be sufficient for anyone with a clue. Bonus points if you install
any industry standard benchmarks to measure things like memory/disk
io/networking latency/bandwidth.

But, in the end I get it. People talk about all kinds of crap that isn't true
about the mainframe, but that doesn't matter. What companies are getting when
they buy a zeries from IBM is a software stack with a 99.99% future
compatibility statement. That means the millions you invest in developing
software today will still work two decades from now. IBM isn't going to pull
the rug out from under you when the latest OS/language/etc shows up. That is
why its possible to run JCL/COBOL/etc written decades ago without change on
modern machines. For companies that use computers to assist their main line of
business (rather than being the main line itself) this is an extremely
valuable feature.

~~~
nickpsecurity
"What companies are getting when they buy a zeries from IBM is a software
stack with a 99.99% future compatibility statement. "

That is the greatest benefit. I think there's a potential market for a company
using something modern (and maintainable) that offers same benefit. Especially
if it can work side-by-side with mainframes and/or popular stacks.

