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Why Recommended Commarea size is 24K

 
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hiravibk
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Joined: 14 Dec 2008
Posts: 103
Location: India

PostPosted: Fri Jun 03, 2011 3:53 pm    Post subject: Why Recommended Commarea size is 24K
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Hi All,

The maximum COMMAREA size i believe is 64K. But i read that IBM recommends that the commarea size be limited to 24K to 32K. Any reason why this recommendation?

Thanks
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valyk

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Joined: 16 Apr 2008
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Location: South Carolina

PostPosted: Fri Jun 03, 2011 4:03 pm    Post subject:
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The maximum Commarea is 32k. The reason is that orignally CICS was built for 16 bit architecture, and there were 15 bits for addressing storage. 2^15 is 32k.

For applications that require a commarea larger than 32k, use channels and containers.
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Bill O'Boyle

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Joined: 14 Jan 2008
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Location: Atlanta, Georgia, USA

PostPosted: Fri Jun 03, 2011 4:24 pm    Post subject: Reply to: Why Recommended Commarea size is 24K
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Actually, the maximum-length is 32763 as a signed binary-halfword.

Bill
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Robert Sample

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Joined: 06 Jun 2008
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Location: Bellevue, IA

PostPosted: Fri Jun 03, 2011 5:14 pm    Post subject:
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Quote:
The maximum COMMAREA size i believe is 64K.
Your belief is wrong. As has been pointed out, the limit is half that (minus 1). And why did you not check this in the manual (link at the top of the page)? It is quickly and easily found in the CICS Application Programming Reference manual -- not to mention a search of this very forum would find a number of topics discussing the DFHCOMMAREA limit.

I believe the 24K recommendation is to allow for system headers and other overhead.
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hiravibk
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PostPosted: Fri Jun 03, 2011 5:36 pm    Post subject:
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Thank you so much. That helps!
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Bill O'Boyle

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Joined: 14 Jan 2008
Posts: 2502
Location: Atlanta, Georgia, USA

PostPosted: Fri Jun 03, 2011 6:04 pm    Post subject: Reply to: Why Recommended Commarea size is 24K
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As Robert had said, this subject has been discussed quite extensively.

For more hits, instead of DFHCOMMAREA, search this forum for EIBCALEN.

Bill
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