Ah, who was before ? The egg or the hen ?

So, Alfredo, you wrote :

> MPE (even MPE-V) has a very rich file system (which, if people
> involved with other OSs took the time to study, would benefit
> by copying MPE's ideas into their pet OSs :-)

MPE V/E did not have the Transaction Manager, perhaps the most beautiful
piece of software I've ever seen. However, it did have PRIV files and lots
of other nice features.

> IMAGE just happens to take full advantage of such a wonderful
> file system.

Correct. On MPE/iX, it uses prefetching to (what I think is) the fullest of
its capabilities. Prefetching works even better than disk (disc ?) caching,
without the same tremendous CPU hit. That helps you achieve performance you
can only dream of in other environments.

> The fact that all IMAGE files are *privileged* files certainly
> provides a good basis for perceiving that MPE treats IMAGE files
> as "special", because privileged files are, by definition,
> "special".  But privileged files are just one "category" or
> "type" or "class" of MPE files.  The MPE file system has many
> other powerful features.

Not only Image files. Allbase and other SQL files are privileged too.

> Come to think of it, there is nothing truly "special" about
> privileged files (ANY file can be made privileged by simply
> changing its file code to a negative number -- but this requires
> PM capability and, so, is not a trivial matter for the casual
> hacker :-)

My dear Alfredo, I have to dissent on this one. Since a hacker has somehow
gotten access to your system, that means that she/he has been able to bypass
a few of MPE's usual security features. In turn, that means your hacker is
most lileky aware of what PM is, and certainly has gotten PM privileges. As
a consequence, your hacker will be able to crack open all PM data
structures, including TurboImage databases.

> The beauty of the "privileged file" concept is that only privileged
> processes can "open and access" such files and it is up to
> the system manager to decide WHICH processes (and which accounts
> and which groups and which users) have PM ("privileged mode")
> capability and which do not.

That's only partially true. All TurboImage code runs privileged. It's not a
sin - it's basically what keep TurboImage data structures protected. And
it's no big deal to run PM code within a non-PM program. In fact, MPE
handles that gracefully for you.

So, while it's true to say that a system administrator may choose which code
runs PM and which does not, it's not true for Image - it's all PM. And
everyone knows PM code can be executed by non-PM programs, which is the case
for TurboImage code, incidentally. in fact, lots of MPE OS code is actually
PM, and it runs without a glitch from non-PM programs.

> I don't want to bore everyone by waxing poetic about MPE's file
> system.  Hopefully, this little discussion on ONE aspect (the
> "privileged" category) will give you a taste.
>
> So, both Christian and John are correct.  MPE (and HP-UX and
> Linux and MS Windows and Mac OS) may or may not have any idea(s)
> regarding databases.  MPE just happens to provide a much richer
> file infrastructure that good database designers (take Fred White
> as an example) can exploit to its fullest advantage.

Another example of what Alfredo says is that most Un*x flavors only have 1
type of file - bytestream. MPE has 4 main types : fixed, variable,
undefined, bytestream. I could give truckloads of other examples of the
richness of MPE as far as file handling is concerned. Temp files ? MPE has
them. Spool files ? MPE has them. Message files ? And so forth.

> Now, on to a tough challenge:  How did the topic "HP Press Release
> about hp3000" change into "MPE's rich file system"?  I wish that
> *all* marketing topics would evolve into technical topics :-)

So what's that ? A last-ditch attempt by a handful of techies to
successfully promote the technical killer advantages in non-technical
circles ?

Christian "MPE Evangelist" Lheureux

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