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Dibakar

I would like to know why CICS was developed. What problems did it solve.

Dibakar.

kolusu · Posted: Mon Dec 02, 2002 6:27 pm Post subject:

Dibakar,

CICS stands for Customer Information Control System which is a family of application servers and connectors that provides industrial-strength, online transaction management and connectivity for mission-critical applications.

Some of the benefits of CICS are:

CICS is a growing multi-billion dollar business for customers, IBM and the thousands of software companies which support CICS.
CICS handles more than thirty billion transactions per day. Each day CICS processes more than $1 trillion in transactions
More than thirty million people use CICS
CICS can support over nine hundred thousand concurrent users
CICS allows any enterprise to adopt e-business whilst minimizing the exposure to the potential risks of new technology, by use of an evolutionary approach.
CICS allows you to take existing applications to the web with little or no change.
CICS has the internet support you need to build you e-business.
CICS supports numerous application development environments and models including COBOL, PL/I, Java, EJB and Object Oriented (OO), in any combination.
CICS provides unmatched scalability, performance, throughput, reliability, security and data integrity - all essential for e-business.
CICS runs on z/OS, OS/390 and VSE/ESA. CICS API is also available on AIX, Windows NT, Solaris, HP-UX via TXSeries.

Hope this helps...

cheers

kolusu

Hariharan78 · Posted: Mon Dec 02, 2002 11:39 pm Post subject:

Hi ,
Ur post is really helpful to me.

Bye
_________________
S.Hariharan

Dibakar · Posted: Tue Dec 03, 2002 8:33 am Post subject:

Thx kolusu and hariharan,

I would rephrase the question a bit, as my interviewer did, what sort of application you can write using CICS that you can't do by REXX.
I feel that CICS makes it easier, reliable, secure and easily maintainable than REXX. But this guy was not satisfied with this answer. Is there something else or he was just trying to pull my leg.

Dibakar,

Manas Biswal · Posted: Tue Dec 03, 2002 9:05 am Post subject:

It's very difficult to compare CICS with REXX. REXX is a basic language generally used for tools and other such small stuff to make things easier for a mainframe user. They are very seldom(if ever) used in a production environment.
CICS is a robust transaction server.
Well, looking at it very objectively, we may be able to accomplish all the applications that we build using CICS, at a basic level using REXX too.
But the efficiency and performance difference between the two will be very very very large.
REXX does not support concurrency, multitasking, multithreading,re-entrancy, syncpointing (to name a few) as CICS does.

Pardon my hard words - But the question that your interviewer asked was rather absurd, I would say.

Regards,
Manas

Dibakar · Posted: Tue Dec 03, 2002 9:42 am Post subject:

I guess he was trying to see how much grasp I have on CICS concepts which I don't have as I code CICS very rarely so my exposure is only upto few commands. Unfortunately the interviewer could make that out too. Maybe I will need to do some reading.

Thanks,
Dibakar.

kkinney · Beginner Joined: 05 Dec 2002 Posts: 3 Topics: 0

My friend, you were handed a trick question. But first, I will address your immediate question.

The reasons previously mentioned for using CICS rather than REXX are all valid, but being an MVS guy as well, perhaps I can offer a different perspective.

Something important to note is that REXX is a language and CICS is an application framework. They're apples & oranges, but as you'll see later, they aren't incompatible.

REXX, running under TSO, can to some really cool things. But it places more demands on all available resources.
TSO runs in it's own address space and this taxes the system more. All of a CICS region only takes up a single address space. So for a given number of users, CICS is FAR more efficient.

Security is far easier in CICS as it is more of a streamlined environment. This places fewer demands on your RACF people.

CICS has several methods for getting a GUI frontend. TSO has one, and it's so lame, no one uses it.

REXX is interpreted. (translation - "The CPU has to first convert it into machine code before running it.") For the most part, CICS languages are compiled into machine code before getting into CICS, run faster and use fewer memory & CPU resources.

I could go on, but anything I would say would repeat this simple message - For comparable applications, CICS is far more efficient than TSO/REXX.

And now to the trick question. My answer to the interviewer would be, "First, I wouldn't run REXX at all except for small, ad-hoc things in TSO. But if you're fixated on REXX, why not run it under CICS? REXX/CICS has been around for a release or two."
(You may now smack your forehead.)

Dibakar · Posted: Thu Dec 05, 2002 10:27 am Post subject:

Thanks for nice answer. This did explain some advantages which is more understandable for a person who is not much familiar with CICS.

Manas Biswal · Posted: Thu Dec 05, 2002 10:46 am Post subject:

Hi Kinney,

Can you please elaborate on REXX/CICS that you were talking about. I haven't heard of that. Please provide me with some links of the same.

Regards,
Manas

kkinney · Beginner Joined: 05 Dec 2002 Posts: 3 Topics: 0

Please search altavista with keywords "Rexx near CICS" and you will get the desired results.

There are 945 links to references to CICS & REXX -

Edited by site admin to avoid the left and right scroll bar

kkinney · Beginner Joined: 05 Dec 2002 Posts: 3 Topics: 0

To address the original question, "What problem did CICS solve?", you might ask Bob Yelavich (yelavich.com) this question. He attributes the creation of CICS to Ben Riggins, but Bob is who everyone thinks of when you mention CICS.
Bob is a gifted speaker. If you have a chance to hear him speak, go.

I'm going out on a limb, but as best I understand it, CICS was created to allow people in different locations reliable input, browse & update access to a common database. In the late 1960's this was a pretty cool idea.

It must still be cool. Otherwise Microsoft wouldn't still be trying to reinvent it.

This is possible under TSO/REXX, but you'd have to handle all the enqueuing, syncing, rollback, etc youself. Why reinvent CICS when it's there and had been improving for 30+ years?

That's just my opinion,
kk

Abhi · Posted: Sat Dec 07, 2002 3:28 am Post subject:

One thing that has not been mentioned here and the thing that I think is one of the best things about CICS is, it is psuedo conversational... meaning the program is no longer active in the virtual memory (read CICS address space) after it has thrown a map and till the user inputs data and sends the map back. This allows more programs, transactions to run concurrently in the same address space.

Dibakar · Posted: Mon Dec 09, 2002 7:30 am Post subject:

Thanks Abhi,
After reading pseudo conversation, I do see an advantage of CICS over other standard programs which looks difficult to replicate.

DaveyC · Posted: Tue Dec 17, 2002 10:28 am Post subject:

Of course, pseudo-conversational programs are all the go in CICS. But in ISPF all programs are conversational, and time sharing makes it reasonably effecient.
_________________
Dave Crayford

Dibakar · Posted: Wed Dec 18, 2002 1:21 am Post subject:

Some years ago I wrote, intentionally, a REXX or CLIST (I don't remember which one) program going into infinite loop and not doing anything else. It took 100% CPU and brought mainframe down. Can't say exactly what happened but no user was able to do anything until system people cancelled my program. Now I wonder why this happened, isn't it against time sharing? Can it happens in CICS?