I'm assuming you want general information about mainframes, and
computers that run the OS/390 operating system. Your question is
rather broad, but if that's what you intended, there's a wealth of
information on the web.
The High Tech Dictionary
(http://www.computeruser.com/resources/dictionary/)defines a mainframe
like this:
"...A large and expensive computer with the ability to support
hundreds or thousands of users simultaneously..."
That wasn't very helpful, but the next one was perfect for our needs.
The following definition, which covers the gamut of what I THINK
you're looking for is from TechWeb's Tech Encyclopedia. I've taken the
liberty of duplicating it below because it is so good. It also
specifically references the OS/390.
(http://www.techweb.com/encyclopedia/defineterm?term=mainframe)
"A large computer. In the "ancient" mid-1960s, all computers were
called mainframes, since the term referred to the main CPU cabinet.
Today, it refers to a large computer system.
There are small, medium and large-scale mainframes, handling from a
handful to tens of thousands of online terminals. Large-scale
mainframes support multiple gigabytes of main memory and terabytes of
disk storage. Large mainframes use smaller computers as front end
processors that connect to the communications networks.
The original mainframe vendors were Burroughs, Control Data, GE,
Honeywell, IBM, NCR, RCA and Univac, otherwise known as "IBM and the
Seven Dwarfs." After GE and RCA's computer divisions were absorbed by
Honeywell and Univac respectively, the mainframers were known as "IBM
and the BUNCH."
IBM has the lion's share of the mainframe business, and Hitachi Data
Systems and Amdahl are its major competitors, making
System/390-compatible computers (see IBM-compatible mainframe).
Unisys, Sun and others make mainframe-class machines, but run under
proprietary or UNIX-based operating systems, not IBM's OS/390.
There Is a Difference!
One might wonder why mainframes cost up to several millions of dollars
when their raw megahertz (MHz) or MIPS rates are no higher than a PC
costing 1,000 times less. There are reasons. Firstly, in a small
computer such as a PC, the CPU does almost all the processing. Unless
direct memory transfer (DMA) is used, the CPU is also involved with
getting data to and from the peripherals, the most time-consuming part
of the operation.
A mainframe provides enormous amounts of throughput by offloading its
input/output processing to a peripheral channel, which is a computer
in itself. Mainframes can support hundreds of channels, up to 512 in
some models. Mainframes also have multiple ports into memory and
especially into high-speed caches, which can be 10 times faster than
main memory. Additional computers may act as I/O traffic cops between
the CPU and the channels and handle the processing of exceptions (what
happens if the channel is busy, if it fails, etc.). All these
subsystems handle the transaction overhead, freeing the CPU to do real
"data processing" such as computing balances in customer records and
subtracting amounts from inventories, the purpose of the computer in
the first place.
Secondly, the internal bus transfer rates of mainframes are also
higher than small computers. A 800MHz Pentium has a data bus that runs
at 100MHz, but a 200MHz mainframe may have a data bus that also runs
at 200MHz, twice as fast. The multipliers add up. Twice the bus speed,
10 times the cache speed, perhaps 32 or 64 overlapped data transfers.
Multiply one times the other, and the combination of fast buses, fast
caches, multiple memory ports and independent channels and subsystems
produces a powerful machine.
Thirdly, much of the hardware circuitry in a mainframe is designed to
detect and correct errors. Every subsystem is continuously monitored
for potential failure, in some cases even triggering a list of parts
to be replaced at the next scheduled maintenance. As a result,
mainframes are incredibly reliable. The mean time between failure
(MTBF) is generally 20 years!
In addition, mainframes are highly scalable. Based on symmetric
multiprocessing (SMP), mainframes can be expanded by adding CPUs to a
system or by adding systems in clusters.
They're Here to Stay
Once upon a time, mainframes meant "complicated" and required the most
programming and operations expertise. That is no longer. Networks of
client/server-based PCs make mainframes look easy. Nothing is more
complicated than the Windows environment. Add NetWare, throw in a
little UNIX for good measure, and you have enterprise computing at its
most complex ever.
With more than two trillion dollars worth of mainframe applications in
place, mainframes are here to stay, and their centralized
architecture, which is the easiest to manage, may just be the wave of
the future!"
Now lets assume you want information about the OS/360 in particular.
For starters, check out http://www.qrx.de/. This is an incredible site
that has a comprehensive textbook on OS/390 as well links to
additional sites. You can even download a copy of the operating system
for your personal use. Most of the information on this site is
available in English although there are certain parts available in
German only.
The following link is the IBM official web page on OS/390:
http://www-1.ibm.com/servers/s390/os390/
This is a great site for general information. Part of the copy reads:
"The OS/390 operating system includes and integrates functions
previously provided by many IBM software products." Some of the
information links from this page include:
e-business
OS/390 overview (summaries, specs, ref guides, and more)
Parallel sysplex
z/OS and OS/390 security
S/390 software usage pricing
z/OS and OS/390 calendar of events
Datatrain (http://www.datatrain.net/) has training courses on os/390
you and your programmers can sign up for and take online.
Another great resource is http://search390.com. This is a OS/390
portal that also provides training and an "ask-a-tech" resource. This
looks like a one-stop resource based a quick review. If you'll click
on "best web links" at the top, you'll be taken to a long list of text
resources, background, and resources on OS/390.
A review by Gartner Company on the latest v2, r8 is available at
http://techupdate.cnet.com/enterprise/0-6133429-723-3894999.html?tag=st.jp.6133429-720-3894999.fr.6133429-723-3894999-1641505
(If you have a problem with this link go to zdnet.com and do a search
on OS/390. You may have to paste the entire link into your browser)
This article provides an analysis of the current platform, a list of
its strengths and limitations, and some interesting conclusions.
To be totally frank, I could be totally off base since your question
was rather broad. If that's the case just give me some clarification
and I'll go back to work!
http://www.qrx.de/
http://www-1.ibm.com/servers/s390/os390/
http://www.datatrain.net/
http://search390.techtarget.com/
http://techupdate.cnet.com/enterprise/0-6133429-723-3894999.html?tag=st.jp.6133429-720-3894999.fr.6133429-723-3894999-1641505
http://www.computeruser.com/resources/dictionary/
http://www.techweb.com/encyclopedia/defineterm?term=mainframe |
