AS/400 internals

Hi,

I was asked about the virtual memory management of the AS/400. Tough I've
read the work management book, other performance related IBM publications
and the book of Frank G(od) Soltis I still don't know how does it work. For
example, how does the internal code decide which pages to bring in/out?
Does OS/400 make statistics of the paging characteristics of the individual
jobs or threads (as VM does, for example)? What does the LIC do when I turn
the expert cache on/off? AS/400 uses all DASD for paging: do objects
continously change their physical location on disk due paging? Or the
object's pages are stored somewhere when the object is created (or
extended) and do not move anywhere.

Another topic I'd like to hear about is the scheduling of threads (tasks).
For example: what happens if a few high priority tasks keep the CPU busy,
and don't permit lower priority task to run? It is theoretically possible
that some tasks never run, or the system has some built-in mechanism to
raise the priority of each ineligible task?

                    Budai Benjámin
                          (ICSS Kft. - Hungary)


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