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Discrepancy between source code and output.


IBM Mainframe Forums -> COBOL Programming
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I?aki Viggers

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Joined: 18 Jun 2005
Posts: 8

PostPosted: Wed Jun 22, 2022 6:22 am
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This is a follow-up of another question.

This simple program creates an output member, writes a record, and closes the member:

Code:
000001        IDENTIFICATION DIVISION.             
000002        PROGRAM-ID. 'IVCBL2'.                 
000003        ENVIRONMENT DIVISION.                 
000004        INPUT-OUTPUT SECTION.                 
000005        FILE-CONTROL.                         
000006            SELECT FHANDL ASSIGN TO UT-S-ODS1
000007              ACCESS MODE IS SEQUENTIAL.     
000008        DATA DIVISION.                       
000009        FILE SECTION.                         
000010        FD  FHANDL LABEL RECORDS ARE OMITTED.
000011        01  RECOR.                           
000012        05  FIELD1 PIC X(80).                 
000013        PROCEDURE DIVISION.                   
000014               MOVE SPACES TO FIELD1.         
000015               MOVE 'ASDFG' TO FIELD1.       
000016               OPEN OUTPUT FHANDL.           
000017               WRITE RECOR.                   
000018               CLOSE FHANDL.                 
000019               STOP RUN.                     

The program purports to run successfully, but the contents of the member are
Code:
****** ****ZAP****AUTOSAVE********** TOP OF DATA ******************************
000001   óÌ                                                                   
****** ****ZAP****AUTOSAVE********* BOTTOM OF DATA ****************************

which does not resemble at all what is coded on lines 14 & 15 of the COBOL source.

What am I doing wrong?
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sergeyken

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Joined: 29 Apr 2008
Posts: 1533

PostPosted: Wed Jun 22, 2022 8:36 am
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Where is your JCL?


COBOL code itself cannot create a library member.

For COBOL, usually the member of a PDS dataset (a library) is defined in the corresponding DD statement.

Another way: using CALL to a specific (non-COBOL) function, or utility program, which are able to operate with PDS datasets, and "create new members".
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Phrzby Phil

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Joined: 31 Oct 2006
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Location: Richmond, Virginia

PostPosted: Wed Jun 22, 2022 10:09 am
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It's been a long time, but I think your problem is that you attempt to populate the output record before OPENing the file.

To do it this way, you would populate a WORKING-STORAGE field, OPEN the file, and then do a WRITE FROM the populated field.
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I?aki Viggers

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Joined: 18 Jun 2005
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PostPosted: Wed Jun 22, 2022 6:55 pm
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Phrzby Phil wrote:
It's been a long time, but I think your problem is that you attempt to populate the output record before OPENing the file.

Thank you! Yes, you're right. I got it now.

I am liking COBOL, but as a mainframe neophyte with a C/RPG/SQL/x86-asm background I'm noticing multiple counterintuitive minutiae about COBOL and mainframe.
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I?aki Viggers

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Joined: 18 Jun 2005
Posts: 8

PostPosted: Wed Jun 22, 2022 7:06 pm
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sergeyken wrote:
Where is your JCL?

COBOL code itself cannot create a library member.

For COBOL, usually the member of a PDS dataset (a library) is defined in the corresponding DD statement.

I omitted the JCL for brevity, but it is quite similar to the one I posted in the referenced question where you helped me. What Phrzby Phil pointed out helped me solve the particular issue that originated this post.

Quote:
Another way: using CALL to a specific (non-COBOL) function, or utility program, which are able to operate with PDS datasets, and "create new members".

Good to know, although I'm still much of a beginner to try this approach icon_lol.gif
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Phrzby Phil

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Location: Richmond, Virginia

PostPosted: Wed Jun 22, 2022 7:15 pm
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The buffer(s) are allocated when the OPEN is executed.

I'm thinking that by trying to populate the FD record before the OPEN, you might sometimes get a protection error.

Anyone have an opinion on this?
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Phrzby Phil

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Joined: 31 Oct 2006
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Location: Richmond, Virginia

PostPosted: Thu Jun 23, 2022 10:18 pm
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I?aki Viggers -

One other thing I might as well mention since you are new to COBOL.

In COBOL and most languages, there is no need to space out a character field before moving a smaller length value to it. The move will fill the remaining bytes with spaces.

So your MOVE SPACES below is not needed:

Code:

MOVE SPACES TO FIELD1.         
MOVE 'ASDFG' TO FIELD1.


It does not hurt, but it is clutter.
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Robert Sample

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Joined: 06 Jun 2008
Posts: 8633
Location: Dubuque, Iowa, USA

PostPosted: Sat Jun 25, 2022 1:27 am
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Quote:
I'm thinking that by trying to populate the FD record before the OPEN, you might sometimes get a protection error.
For a batch job, I doubt a protection error could occur since the allocation occurs somewhere in the address space memory.

The COBOL Programming Guide manual specifically tells you not to do what you did:
Quote:
Data items defined in the FILE SECTION are not available to PROCEDURE DIVISION statements until
the file has been successfully opened.
And note the quote does not say that the OPEN statement was executed but that the file was successfully opened (so you need to check the FILE STATUS code to be 00).
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