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Expert Question of the Week
September 17, 2001
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FEATURED TOPIC: Web Integration
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Welcome to Search390's Expert Question of the Week newsletter.
Remember, no question is too simple for Ask the Experts! If you have
a 390-related question, send it to [EMAIL PROTECTED] Selected
questions will be answered by our experts.
This week's question was answered by Jim Keohane, search390's Web
Integration Expert.
THIS WEEK'S QUESTION:
Q: Is HLASM code useless for Web enabled applications? I find
zillions of code samples, examples, information and doc for
communicating between OS/390 apps and an OS/390 Web server. Problem
is they are all C++, Java (even COBOL) oriented. What's an asm
programmer to do?
A: No. Get back from that ledge. All is not lost. Think happy
thoughts.
Web apps talk to each other over sockets. Assembler programs have
been talking over sockets since the 80's. There's EZASMI MACROs
(Sockets Extended Assembler Macro Interface). Prior to that, and
still usable to a degree, were IUCV and VMCF (VM and MVS) macros. The
newer BPX..... services also work fine but require an LE environment.
That can be done from assembler.
>From within environments like CICS there is no problem writing web
aware apps in assembler. If you need to talk various web protocols
(HTTP/HTML, etc.) they are supported by, I think, EXEC CICS DOCUMENT
and other facilities.
A complicated web app may have to communicate in various protocols
that are very complicated to write yourself, and so you would use a
support library. That support library may also require LE. That
library may also be packaged as a DLL which, until recently, was only
usable from IBM C/C++. Latest HLASM provides features to have
assembler load/call these DLL's.
Take heart. Many of these web operations might run very efficiently
on unix and windows and Mac workstations but, when ported to OS/390
wreak havoc with their unexpectedly high CPU impact. There are many
reasons for this. C was not targeted for a CICS system with
storage-to-storage instructions. It tends to underuse these
instructions and overuse byte-by-byte logic. IBM added LSA (Logical
String Assist) to ES/9000 models years ago and most non-emulated
mainframes today have it but few shops make use of it. It can spee up
C software after a recompile.
Memory management is more of a hit on OS/390 than on other boxes.
S/390 instructions like TR, TRT, TRE are rarely used in C compared to
what an assembler programmer would do.
It is conceivable C/C++/Java apps will call assembler routines for
cpu-critical processing. It's not uncommon to see assembler code 10
to 25 times faster than perfectly acceptable C/C++ code. In fact,
that's how I earn my living. A profiler like Strobe determines the
CPU culprits and I rework, redesign, tweak the logic involved and,
where needed, drop into inline assembler or actual assembler
subroutines.
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Do you have a question for Jim? Jim is not only search390's Web
Integration Expert, but he is also the moderator of our Developer and
Executing E-Business discussion forums.
If you'd like to send Jim a question via our Ask the Experts feature,
click on this url:
http://search390.techtarget.com/ateQuestion/0,289624,sid10_cid365817_tax285032,00.html.
If you'd prefer a quicker response, you might want to post a question
in one of our discussion forums. To do so, go to:
http://search390.discussions.techtarget.com/WebX?[EMAIL PROTECTED]^0@/search390
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