Re: what's a mainframe

On 9/11/2024 7:05 PM, John Levine wrote:

According to Lars Poulsen  <lars@beagle-ears.com>:

On 9/11/2024 9:21 AM, John Levine wrote:

  I think you'll find a pattern since the
CDC shock of making CPUs fast enough to keep the RAM and I/O devices busy while having
the error checking and recovery features so the systems keep running for years at a time.

>
So do these systems not require security patches?
Or do they apply PTFs to the running system? (reliably?)

 They don't just update the software, they swap out entire hardware subsystems while the
overall system keeps running.

The multiprocessor systems I worked on were small (-4 CPUs), and the processors shared one memory space, i.e. one OS image. But yes, I have seen the descriptions of how the Z systems allow a "workload" (i.e. a job?) to move from one processor to another, and the cluster has spare processors to move them to.
My brother spent the latter half of his career in that world, in operations groups supporting banking systems. In departments that changed owners several times even as the customers remained the same. At one point his group was part of IBM, then it became Maersk, then a bank consortium, then spun out as a standalone company, which was then acquired by an Italian holding company. His wife did software for bank card processors ... same kind of shifting ownership.
I spent my life in smaller engineering companies, doing embedded micro work and device drivers for custom peripherals in various minicomputer OSes and RTOSes.