Flat file, same field, different positions

[Buck Calabro <Buck.Calabro@xxxxxxxxxxxx>]

I have an EDI-like flat file where I have standard data elements which occur
in different places depending on the record type.  The fields are all
packed.  The existing implementation simply maps them all into one set of I
specs in RPG III, and has IGNDECERR(*YES) set.

Iflatfile  NS  02   22 C                          
I          OR  01                                 
...
I                             P   31   31 0SEA500 
I                             P   40   40 0SEA625 
I                             P   46   46 0SEA364 
I                             P   30   30 0SEAUSF 
...

There are dozens of fields on each record type.  I'm doing maintenance and
want to make this RPG IV so I can use reasonable names, etc.  Unfortunately,
I need to use FIXNBR(*ZONED *INPUTPACKED) in order for it to run as-is.
This generates tens of thousands of messages in the job log as each
'invalid' number is 'fixed'.  Understand that for a 500 record type, the
program only references the 500 fields.

I want something like:
     d struc0001       ds                  
     d  sensType                      3p 0
     d  sensID                        7p 0
     d  roType                        3p 0
     d  roID                          7p 0

     d struc0360       ds                  
     d  sensType                      3p 0
     d  sensID                        7p 0
     d  roType                        3p 0
     d  roID                          7p 0

But that won't compile because the same field is in a different DS.  I could
use qualified, but as far as the calculations go, eval sensType=sensType0001
isn't much different from eval sensType=struc0001.sensType.  I still have to
copy all the fields by hand as it were.

I have two goals:
1) I don't want to use FIXNBR; so I'm separating the fields 
   into separate structures
2) I'd rather use one set of names to describe the same fields;
   not SEA500, SEA625, SEA364, but SEA.

Since the input data is packed, I can't readily use the old standby I specs
because I can't specify the hex codes needed to recognise the packed fields.
I'm stuck, aren't I?  It gets worse when having to support this back to
V4R5.  Just thought I'd post a tale of woe on a rainy Northeast US Friday.
  --buck