Re: AS/400 and DB2 vs. Unix and Oracle

From: <crobato_at_kuentos.guam.net>
Date: 1996/01/23
Message-ID: <4e21hj$21m_at_lehi.kuentos.guam.net>#1/1


In <DLJywz.HBr_at_eskimo.com>, salvo_at_eskimo.com(Marc Salvatori) writes:
>In <4dcacb$co1_at_lehi.kuentos.guam.net> Christopher Robato wrote:
>> You should see how progressive OS/400 is. How about an object oriented
>> design and architecture, with microkernel.
>
>OS/400, an object-"based" kernel, I can understand. But object-oriented?
>Hmmmm. Please expand on your thoughts here. An object-oriented kernel
>should allow you to add modules without the need to re-IPL, let alone
>reconstruct the kernel package.
>

First of all, the word "kernel" does not exist in the AS/400 language. I'm sure there should be such a thing called a kernel deep inside the AS/400, and the thing I know closest to that would be the Machine Interface. So it's really hard to say where the kernel ends or begins. The only time the term kernel is used, is with the current IBM Workplace microkernel version used on the RISC AS/400s (OS/400 v3.6 and above).

And yes, modules are added on the fly without rebooting the machine unless it involves changes in parts of the operating system that can be considered 'kernel'.

The new Microkernel version appears very much the same as the CISC OS/400 v3.1 from the wrappers, and older AS/400 CISC software, like those working under version 2.x of the OS, will run directly without any code changes, on the RISC version of the OS, assuming observability is built to the code (what AS/400 software that isn't?) Just install your current software; no need to call your VAR for the RISC upgrade of your programs.

In fact, the RISC version looks practically the same as the CISC version, and every part and module has the same behaviour that I think they are literally the same. Only the 'kernel' is switched.

The term "object oriented" also applies to the very paradigm and concepts of the OS/400 itself. Everything is treated as an encapsulated object. Everything has an object header tag, which includes among others, the owner of the object, the security status of the owner, which is inherited by the object. Adding and configuring devices in the AS/400 are derived from a base class of preconfigured objects and templates, which the device inherits its characteristics from. New users are configured and inherit the qualities from preexisting classes of users.

One interesting aspect of the architecture is that OS/400 does not use byte addressing, which MVS and OS/390 uses (and just about every OS in this world.) Instead, it uses "object" addressing. Pointers in OS/400 never point to byte addresses; rather, they point to objects (a 128 bit address decoded by the microcode in the Machine Interface.) The objects can reside anywhere in the vast "single level store" memory space or universe---the AS/400 does not make a distinction on what is RAM or main memory, and what is virtual memory. It will address whole arrays of disks like they are RAM in a single contingous space of memory.

Rgds.

Chris

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Chiusagi Tsukino/Sailor Chibimoon *****crobato_at_kuentos.guam.net***** Received on Tue Jan 23 1996 - 00:00:00 CET

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