Question on CPYTOIMPF performance

25 pts.
Tags:
AS/400
CPYTOIMPF
I create 2 programs, both of which use CPYTOIMPF to format a list of AS400 PFs to character delimited files. The difference between them is: one formats files to qtemp(PGM A), while the other one formats files to a library other than qtemp(PGM B).
I called the 2 program separately to format about 90 files, with total about 8 million records. Both of the programs consumed more than 1300s CPU time, while PGM A used about 5% less CPU time than PGM B. I have tryied several times and the result is similar.
May I know why CPYTOIMPF to qtemp is faster than copy to other library?
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Software/Hardware used:
IBM AS400 CL(V5R4)

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<i>And jobs run simultaneously</i>

This may be part of your problem. Try running them separately and see what happens. You might want to look at what types of other jobs are running on your system.

Also I did not see where you say whether you are running these jobs as interactive or batch.

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  • TomLiotta
    First, is this a test that you have repeated a few times? Have you signed off/on between tests? Have you run to QTEMP followed by running to "other than QTEMP", and then done the tests over again in the opposite order? CPYTOIMPF uses a lot of SQL inside. You can see indications when running under debug. If temporary indexes or access paths are created, then they might still be available when the second set of tests are run. That's a big reason for both multiple tests and changing the order of tests. QTEMP is scoped to the job. I've never looked into this, but it seems possible that authority tests against QTEMP might be potentially faster than against "other than QTEMP". Maybe these can run a little faster to QTEMP because there some overhead items that are reduced. No answer, just some areas to think about. Tom
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  • Paranoiawire
    Hi Tom, Thanks for ur advice. In fact the testing is done by submit 2 jobs calling the 2 program separately. And jobs run simultaneously. I think the 'reduced overhead item' may explain this issue.
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  • Paranoiawire
    Tom, just about the 'overhead item', can you show me some example of these items?
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  • TomLiotta
    ...‘overhead item’, can you show me some example of these items? Just as an example, review the authority-checking flowcharts in Chapter 5, "Resource Security" of the Security Reference book, topic "How the System Checks Authority". Depending on how many elements must be checked, how many paths are taken through the algorithm, every access to QTEMP in a job might simply be 5% faster than the same kind of access to "other than QTEMP". Authority checking is an overhead to your programming. It's going to happen no matter what. All you can do is influence how it happens. Whether or not it has anything to do with the difference in times...? Who knows? I don't know of any benchmarking that anyone has done to see if QTEMP can be used more efficiently than other libraries. Authorities are definitely an area that makes a performance difference. If you aren't doing it already, try changing your SBMJOBs to run under an *ALLOBJ user. Tom
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