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Perferred calling method?

 
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Josh Keller

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Joined: 08 Oct 2007
Posts: 36
Location: Columbia, SC

PostPosted: Tue Dec 13, 2011 2:27 am    Post subject: Perferred calling method?
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When I'm calling an external routine (cobol or otherwise) in a REXX, I usually program an ISPF SELECT PGM statement. But I'm also aware I can just issue a call directly.

Question: Which is preferred / better / has less overhead?

Code:
"ISPEXEC SELECT PGM(MYPROG)"

"CALL 'MY.LOADLIB(MYPROG)'"

"CALL *(MYPROG)"

My assumption is that the ISPF SELECT has more overhead, but I'm not 100%. I'd figure one of you wise "older" guys would have some proven insight.
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Akatsukami

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PostPosted: Tue Dec 13, 2011 2:41 am    Post subject:
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Overhead or not, note that using an ISPF service of course implies that ISPF is active.
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enrico-sorichetti

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PostPosted: Tue Dec 13, 2011 7:27 pm    Post subject: Reply to: Perferred calling method?
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IMHO for REXX <application> performance should not be the main concern
just use reasonable good sense (for example frown upon large stems)
as far as <calling> load modules the best flexibility is usually achieved by the Address <environment> construct as described here
http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/ikj4a370/2.5.9?ACTION=MATCHES&REQUEST=linkmvs&TYPE=FUZZY&SHELF=IKJ4BK90&DT=20060626210253&CASE=&searchTopic=TOPIC&searchText=TEXT&searchIndex=INDEX&rank=RANK&ScrollTOP=FIRSTHIT#FIRSTHIT
great interface for parameter passing, see for example the IGGCSI interface
and the overhead of the different methods for <calling> a program should not be usually a concern

the only method to avoid , unless ISPF services are needed, is the ISPF SELECT approach
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Pedro

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PostPosted: Wed Dec 14, 2011 7:25 am    Post subject: Reply to: Perferred calling method?
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Code:
"CALL 'MY.LOADLIB(MYPROG)'"

"CALL *(MYPROG)"


Between those two, my preference is to have a setup exec that allocates the right application libraries and then later in the application logic use
CALL *(myprog).
It is a maintenance concern rather than performance.

1. if the setup is actually in linklib, then the rexx program can run without changes.

2. if the application is distributed to other systems, then the rexx program can run without changes. Otherwise, you might have RACF access problems.

3. You want the customization to be done in a short setup exec, rather than have the installer search and make changes throughout your rexx programs.
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