"OVERLAY" in dds

[FKolmann@xxxxxxxxxxxx]

Danny Oentung wrote:

> The problem is because some of my programs  need a 2 or three variable
>data structure(the same one) in my program at the same time so I have to
>make/maintain about 3 copybook of that data structure...which is all the
>same except that the subfield name of each one of them i change accordingly
>it's data structure name.
>example:
>
>DQSMFRecord DS 
>D/COPY $VISMFQ 
>DLSMFRecord DS 
>D/COPY $VISMFL 
>
>the content of $VISMFQ and $VISMFL is the all the same except the name of
>the subfield i have to change the first part to Q and another to L.
>I know i can do that in DDS (physical file) using PREFIX(xx:y) keyword, but
>how about the overlaying fields or if i want to define two fields that refer
>to one position only like what i can do in overlaying keyword.
>Do i have to maintain all these copy books??(not integrated)or is there
>other way....If u have any opinion please help me....and thanks for all.

The copy books is a good idea, but surely you don’t need
to maintain  3 or 4 DDS each with 250 fields.

I would use the external definitions to define most of the fields
Then the /COPY has only  overlays and/or overlaps .
I use a method like this for arrays as DDS does not define arrays.

DQSMF  DS EXTNAME(physical file) 
D                                     PREFIX (Q)        
D/COPY $VISMFQ 
DLSMF  DS EXTNAME(physical file) 
D                                     PREFIX (L) 
D/COPY $VISMFL 

Frank Kolmann

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