RE:TIMI

RE:     TIMI

Dave

TIMI It's a term. for .........
The AS/400 is a layered arch.  By that I mean that a layer only communcates
with the layer directly below it.  For instance,  In our applications we
can only(normally) communicate with the OS/400 using various commands.
Well,  These commands call programs which communicate with layers below them.
and so on down to the actual hardware. 

 Example; 98% of the OS/400 system
code(on a CISC 48bit machine) doesn't know that there isn't 281 trillion 
bytes of disk space available.  Only the very lowest part of the OS really
knows that there is a differnce between virtual addresses and physical DASD
addresses.  If a change is made in one layer of the OS,  only the connections
directly above and below it are involved.  No rippleing(?)effect of changes.

If IBM changed the programs that really run when you key in CPYF, you 
would never know it as long as the interface(command parameters) didn't 
change.  This is a positive effect of a layered arch.  As a matter of fact
most everything has changed over the last 20 years of the OS(the system
38 was announced in 1978.  What was the SYS/38's OS called ???  I give you
a clue,  what do the system message ID's start with that you monitor for 
in CL???   If you answered CPF you would be correct.  It stood for 
Control Program Facility.  As another matter of trivial fact,  OS/400 was
originally internally at IBM called XCPF which stood for eXtended CPF.

where was I, Oh ya, Even with all these changes over the years which even 
included moving to RISC and 64 bit addressing,  NONE, I repeat NONE of 
our applications had to be changed or even recompiled.  Try that on any 
other platform(WIN16 to WIN32 what a Joke, rewritten, recompiled, rebound,
and of course NEVER re-debugged<BG>) DEC PDP11 to VMS same thing.  
Name any other platform, same thing.  

Lately on the list there was talk that Date Data Types didn't perform very
fast.  IBM just changed the OS and now they do.  What did you have to 
change in your App.????   Nothing! No recompiles, Nada.  Because you 
are insulated from changes because of the Technology Independent 
Machine Interface TIMI.  (or Layered Arch. Implementation.)


John Carr 
EdgeTech

-------------------------------------------
During a Lunch & Learn earlier today, there was mention of the
TIMI (Technology Independent Machine Interface).
What is this?
What is it used for?

Thanks,
Dave
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