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Mainframe Programming to Make a Comeback?
ajw1976 writes to tell us that IBM has released a series of announcements today "introducing many new software tools, academic programs, and support for outside developers." The new releases are designed to help entice programmers and businesses back to the mainframe. From the article: "The announcements, according to analysts briefed on them in advance, signal a shift from defense to offense in the company's mainframe strategy. Last month, I.B.M. introduced a machine priced at $100,000, about half the previous starting price for its mainframes, which can run up to several million dollars. The announcement of the low-end mainframe was made in China, which I.B.M. regards as a promising market for the machines."
The same is true of their memory subsystems, their disk subsystems, etc., though their backplane performance tends to be second to none. Mainframes are designed for throughput.
Mainframes are capable of staying operational for decades at a time. If you don't want your computer to ever go down and can afford the price, a mainframe is what you want.
One other nice benefit: they've had virtualization figured out on mainframes since the 1960s, so allocating resources is a relatively easy thing to do.
If you're interested in finding out what the older mainframe OSes were like, check out the Hercules IBM mainframe emulator here.
Use 'slashdot stuff' in the subject line in any email you send me if you want to get past the spam filter.
Actually, no. The IBM 370 architecture is open, as a result of an antitrust decree decades ago. There are plug-compatible peripherals and software-compatible CPUs. There's even a good emulator for PCs. It's actually more open that x86 or PowerPC.
To answer your question at least partly, look at something that Sun termed "midframe," the SunFire 6800.
This beast can be physically partitioned into multiple domains. One OS runs on each domain. CPU/Memory boards and I/O boats can be dynamically moved from one domain to another. You can run Solaris 8 in one domain, Solaris10 in another, Linux in a third, and um...*BSD in a fourth. Any of them runs independently of the others. If a board dies, you can deallocate it from a domain, swap it out, and add it back in--all live.
Now multiply that by a LARGE number, add crazy amounts of fault tolerance, and you're getting into the world of mainframes.
"People who do stupid things with hazardous materials often die." -- Jim Davidson on alt.folklore.urban
Your analogy of a 18-wheeler is probably a good one.
It's not the fastest thing in the world, but would you want to haul a load of water main pipes with a Porche?
background.. I'm a mainframe systems programmer..
There are two major aspects of a mainframe. One is the physical hardware (and software), on how it is designed and the other how they are used. The hardware is designed from the ground up to be robust and redundant. Yes it costs thousands (millions?) of dollars for a mainframe system, but with that you get the assurance that the system *WILL NOT CRASH* when an error happens. Instead the system will perform a self diagnosis, make an automated phonecall back to support. Support will send out an engineer (CE) with the replacement parts, which will be replaced while the system is still running (note that there are some (very few) instances where the repair does require downtime to actually perform the repair).
A few years ago, one of our CE's informed me that one of our mainframes had called home with a CPU failure. I asked if he would need to schedule some downtime to replace the card(s). He said ".. No.. we would have to lose 5 more before they would get worried.." Now.. from my viewpoint, I did not see any error, I still see the same number of "Processors" as I did before. What happens is that the system has a bunch of spare CPUs that are kept online. Instructions are run in parallel across multiple CPUs and then the results are checked. If there is a failure (as in the results don't all agree) the system will determine which CPU "failed", perform a diagnosis on that CPU and if it's determined that there is a problem will fence the failed CPU off from use. Note that this is all done under the covers from the operating systems. There is nothing that I need to do to enable or disable this.
Mainframe operating systems behave very differently then the Windows/Unix world. -- Lets take a simple example. An application allocating memory. Under Windows/Unix what happens if the memory allocation fails? -- Answer, the program is handed back control with the hopes that it will test the returned value. On a mainframe by default if there is a memory allocation error, the application will be "abended". Now the program *can* request that if there is an error to allow it to continue by explicitly stating that it will handle the error. This concept is carried throughout the system API. By default the application will be halted if there is an error. Under Windows/Unix the default is to simply return some error flag and hope that the application will handle it.
The way mainframes are used and maintained is a little different. Things are usually not done on a whim. This really isn't due to anything physically different on a mainframe, but more of the "culture". Yes these are big expensive boxes, therefore the company that owns (rents) them wants to make sure they are maintained and running efficently. When changes are made, they are researched and documented with fallback plans. When even minutes of downtime could mean millions of dollars lost, it's well worth the investment in time to make sure that a change is correct. Going back to the 18-wheeler analogy, I suspect that when it's time to do a scheduled maintenance on the tractor there is a lot more testing/verification then you would have done on your family car.
For any organization that may contemplate getting into mainframes -- skip z/OS (MVS). MVS is what most folks dread when they think about mainframes (JCL, pre-allocate datasets, etc.). A modern mainframe (z/990 or z9) running z/VM (5.1 or 5.2) and a bunch of linux guests is *COOL STUFF*. What's really cool is when you need to setup a temporary testing environment -- no problem, just add a half-dozen configuration statements to your "USER DIRECT" and clone an existing guest image to the new machine's disk volumes. Done! Need more memory in that virtual Linux server? No problem, bring up USER DIRECT in XEDIT and edit a single line of text and issue DIRECTXA. Restart the linux guest and now is has more memory. Disk space (volumes) can be added while the Linux systems are running (add as many as you need).
The company I work for hired a person right out of college. Spent about $2500 on him by geting him an IBM Education card which gave him one year of IBM education. This person has grown to fill a very important postion in our technical services department. He started working with CICS and is now performing a zOS operating system upgrade.
I wish we could have more like him.
Mark Jacobs
Time Customer Service
Tampa, FL