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Altering COBOL Load Module Signature Bytes

 
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Bill O'Boyle

CICS Moderator


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

PostPosted: Wed Mar 17, 2010 9:06 pm    Post subject: Altering COBOL Load Module Signature Bytes
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I have a customer, who (up until recently) always compiled their COBOL programs (both Batch and CICS) using the DATA(24) option, because "They always did it this way" icon_sad.gif

Now, they're asking me to alter the load-module signature-byte, which is byte-01, bit-03, to a value of B'1', which represents DATA(31). So basically, this byte would be changed from B'01000000' to B'0110000'.

I have advised them that a zap like this could open a can of worms as well as affect 24-Bit Assembler sub-program addressability (they have several dozen). I've advised them that (as the very least) the Assembler sub-programs need to be relinked as AMODE 31 / RMODE ANY.

Has anyone ever done this load-module alteration before, with success?

I've told them to recompile/link their COBOL programs, specifying the DATA(31) compile option (I believe that's the default) and that will be that.

All feedback is welcome.

Thanks,

Bill
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Robert Sample

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Joined: 06 Jun 2008
Posts: 8118
Location: East Dubuque, Illinois, USA

PostPosted: Wed Mar 17, 2010 9:14 pm    Post subject:
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I've never done such a modification and I suspect it won't work anyway -- COBOL does other things during the compile process that can be affected by the DATA option (generation of address fields for calls to internal programs is just the first thing that comes to mind). They need to bite the bullet and recompile using DATA(31) to resolve everything correctly. If not, I'd recommend at least a couple of months of testing to see what shows up before trusting any such code to production.
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dick scherrer

Site Director


Joined: 23 Nov 2006
Posts: 19270
Location: Inside the Matrix

PostPosted: Wed Mar 17, 2010 10:17 pm    Post subject: Reply to: Altering COBOL Load Module Signature Bytes
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As Wednesday Addams said:

"Be afraid. Be very afraid". . .

d
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MBabu

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Joined: 03 Aug 2008
Posts: 401
Location: Mumbai

PostPosted: Thu Mar 18, 2010 3:14 am    Post subject:
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I think that is a little like expecting to get a fast car by putting a Ferreri bumper sticker on your Yugo. Doesn't make any sense.
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Robert Sample

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Joined: 06 Jun 2008
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Location: East Dubuque, Illinois, USA

PostPosted: Thu Mar 18, 2010 3:38 am    Post subject:
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But Mbabu, the Michelin high-performance tires give the Yugo such a sporty look! icon_biggrin.gif
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mmwife

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Joined: 30 May 2003
Posts: 1592

PostPosted: Sun Mar 21, 2010 9:09 am    Post subject:
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Hi Bill,

You might want to compile a module w/DATA24 and again w/DATA31, then compare the object code, loads, and/or their NOOFF,LISTs.
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