CICS Tuning Techniques.

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AD991
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CICS Tuning Techniques.

Post by AD991 »

Hi,

Could anyone share their experience about the CICS Tuning Techniques? I have already looked at this pdf and still reading it but if anyone has a practical suggestion, it canbe very helpful.


attachment delete ( wrong document )
enrico-sorichetti
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Re: CICS Tuning Techniques.

Post by enrico-sorichetti »

How does the attached pdf relate to CICS tuning ???
cheers
enrico
When I tell somebody to RTFM or STFW I usually have the page open in another tab/window of my browser,
so that I am sure that the information requested can be reached with a very small effort 8-)
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Robert Sample
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Re: CICS Tuning Techniques.

Post by Robert Sample »

It is not clear what you are asking. The Share presentation you posted is more than 10 years old and is not focused at all on CICS tuning but more about CICS sockets usage. Are you attempting to tune a single CICS application? Are you attempting to tune a CICS region with multiple applications executing in it? Are you attempting to tune multiple CICS regions sharing resources (files, applications, terminals and so forth)? Are you attempting to tune a CICS sockets application?

Furthermore, you cannot tune ANYTHING without having a goal in mind -- do you want to tune to reduce CPU usage? reduce end user elapsed response time? reduce I/O counts? something else you have not specified? Each of these tuning goals is perfectly valid under certain circumstances, but they can be somewhat contradictory -- if you tune to minimize CPU time, you usually increase I/O (and frequently end user response times).
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AD991
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Re: CICS Tuning Techniques.

Post by AD991 »

I am sorry, have attacehd the wrong attachment. I was talking about "CICS Performance Guide".


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AD991
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Re: CICS Tuning Techniques.

Post by AD991 »

Robert Sample wrote: Furthermore, you cannot tune ANYTHING without having a goal in mind -- do you want to tune to reduce CPU usage? reduce end user elapsed response time? reduce I/O counts? something else you have not specified? Each of these tuning goals is perfectly valid under certain circumstances, but they can be somewhat contradictory -- if you tune to minimize CPU time, you usually increase I/O (and frequently end user response times).
Hi,

I would like to reduce CPU usage and I/O counts.
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Robert Sample
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Re: CICS Tuning Techniques.

Post by Robert Sample »

As I said earlier, you generally tune towards a goal -- ONE goal. Wanting to reduce CPU usage AND I/O often means you cannot tune at all since reducing I/O frequently means using more CPU time to store data in memory instead of a data set and reducing CPU time means keeping more data in data sets to reduce computational complexity. You may want to think about what is more important and tune that first, then see how the other is impacted.

You also did not say if you are wanting to tune a single application, a CICS region, a set of CICS regions in an LPAR, or what. If you are wanting to tune an application, you also have to know if the application resides in regions using MRO since that will affect where you look for different things.

Having a tool like STROBE available vastly simplifies your tuning efforts as you can see how the code actually works (as opposed to how you think it works -- usually something very different). For CPU usage, tuning usually looks at ensuring all variables used in computations are binary or packed decimal, looking at high-CPU-usage statements in the tool, and minimizing executed code. If you do have a tool and it shows no single statement using more than 5% of the CPU time, then you're not going to be able to do much to reduce CPU usage since there's no good place to start (unless you completely rewrite the program). For I/O usage, the tool also helps identify which COBOL files have the most I/O against them. If you're reading tables, you can move them into memory and reduce their I/O for the program.
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AD991
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Re: CICS Tuning Techniques.

Post by AD991 »

We need to work on a set of CICS region in a LPAR. First we want to concentrate on CPU reduction and I/O is secondary.

There are a lot of mirror transactions and application lies in MRO region.
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Re: CICS Tuning Techniques.

Post by Robert Sample »

Well, you start by analyzing the applications to see where, if anywhere, CPU usage can be reduced. CICS tuning tends to be a very complex topic since there's usually a lot happening, and often there are other pieces contributing CPU time -- such as MQ series and DB2.

With the questions you've asked so far, your organization would be VASTLY better off bringing in a consulting firm to help tune their CICS since it is NOT a topic for someone without experience to attempt without guidance from experienced seniors.
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Re: CICS Tuning Techniques.

Post by AD991 »

Thanks. I was just seekingsome of the documents which you think can be of use.
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