Re: 'Record Format Selector Program': Re: Join & Update

Rob,

A record format selector program was required to facilitate migration of,
commonly used, multiformat files on the S/36.

In migration to the AS/400, each format became a separate physical file with a
multi-format logical over them to simulate what could be done with a single,
program described, file.

Now moving the formats to separate physicals is a good thing, but to minimize 
the
program changes required during the migration, a "format selector" program was
introduced.

So, if the S/36 had an "Open order" file which contained records "header,
"detail", and "total", upon migration, you would have three physicals (header,
detail, total) and a multiformat logical "Open order".

To quote manual GG24-3304-xx "Converting System/36 Environment Applications to
Native AS/400":

<QUOTE>

Format selection information needs to be provided only under certain conditions.
If these conditions do not apply then you do not have to worry about format
selection.

Format selection is only needed if:

1. You are using the file name instead of the record name.
2. The file is a logical file with more than one record format.
3. You are adding records to a file.

Note that if the program is doing updates only (no adds) you do not need a 
format
selection because the program has already read the record and knows which
physical file it came from.

<SNIP>

The format selector program allows you to continue using the file name when
adding a record.

<SNIP>

The format selector program is attached to the logical file.  When your program
writes a record to the logical file, the format selector program examines the
record (after it goes outside your HLL program) and, based upon the content of
the record, supplies the appropriate record name to the logical file.

<SNIP OF SAMPLE CODE>

If you need to provide format selection in any of your programs, we suggest that
you use the first method (replacement of file names in the program by the
underlying record format names) rather than the second method (format selector).
This method is more visible to the maintaining programmer.


</QUOTE>

>
>
> Rob Berendt <rob@dekko.com> wrote:
> >
> > What is a 'record format selector program'?  I've used multiformat
> >  logicals before
> > and don't recall this animal.
> >
> >

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