[Tutor] aBSOLUTE BEGINNER
Alan Gauld
alan.gauld at btinternet.com
Thu Oct 18 11:53:22 CEST 2007
"bhaaluu" <bhaaluu at gmail.com> wrote
> What does that mean... "mainframe technology"?
I'll take a guess at what it means.
A true mainframe is usually one of (or a clone of) IBM
or ICLmainframe hardware running an OS like OS/390. It is
primarily used for large volume data crunching and the
applications use text only screens such as 3270 terminals
running LU6.2 protocol. LU6.2 is somewhat like CGI
on the web(*). A user is presented with a form which they
fill in and submit as a job to the mainframe. The job
executes and presents the results in the shape of
another form. The coordination between transactions
is managed by a system such as IBM's CICS.
(*)I've often thought a mainframe wouldmake the ultimate
web server, but sadly I'll never find out as web apps are
usually considered far too trivial to waste a mainframe on...
For the programmer or 'operator'(sys admin) the system
involves a lot of small executables (programs) each
wrapped up as a "job" in a script written in JCL
(Job Control Language) which will define how much
memory should be allocated, when the job should start,
when it should terminate (regardless of whether it has
finished), its schedulling priority, and so on.
Any scripting in the python sense tends to be done
using REXX, but it still needs to be wrapped in JCL.
Everything is a job on a mainframe.
Mainframe people tend to regard Unix boxes in the
same way Unix guys regard PCs - little more than
grown up toys. Mainframes hardly ever fail, they run
the world's top businesses. But they are expensive,
they are used for data centric rathger than user-centric
applications and so many people working on them
find them a tad dull, or boring... I know I spent a very
instructive year wotking on a mainframe project.
I'm glad I did it, I learned a lot about writing super
reliable programs , but I don't want to do another
one - ever!
Now I may be assuming too much but I'm guerssing
that's what the OP is referring to.
> Python is anything but boring! I doubt we can help you!
Well, Python is much more fun than either REXX or JCL so
learning Python may well bring some light relief.
Alan G.
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