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Am 16.09.2019 um 17:11 schrieb Giuseppe Vitillaro giuseppe-yuD/ahkh7LvrZ44/[email protected]
[H390-MVS]:
>
> On Mon, 16 Sep 2019, Joe Monk [email protected] [H390-MVS] wrote:
>
> > "I guess in pure COBOL '68 that is not possible?"
> >
> > That's correct Peppe. If you read the paragraph it says:
> >
> > "Control bytes are automatically provided when a record *is* written
> and are
> > not communicated to the user when a file is read."
> >
> > Joe
>
> What a shame ;-)
>
> Thanks, a thing to remember.
>
> Now, for handling variable length datasets, possibly spanned,
> in an high level language (I know is more than possible calling
> access methods from assembler) what is left in our MVS3.8j toolbox?
>
> PLI is the more accessible way, if I got it correctly?
>
> Peppe.
>
>
I remember that even in 1990 ca.,
I wrote an ASSEMBLER subroutine to be used with COBOL main programs
to support reading and writing variable length records in COBOL.
The routine was called VLFILE, IIRC, and it supported
up to 10 DD-names with fixed names (like VLF00001 to VLF00010)
which could be opened, read, written and closed using different
subfunctions (function names passed). That is, it had 10 DCBs internally,
to be used via calls by the COBOL program (for up to 10 variable length
files open at the same time, which was more than sufficient).
The parameters looked like this, IIRC:
- function name (OPEN, READ, WRITE, CLOSE)
- file number (a number between 1 and 10)
- pointer to record length field
- pointer to buffer
Don't recall the details, but
for secure processing on read, the caller could specify in the
length field the maximum length which it could accept (that is,
the length of the buffer), and VLFILE could return the number of
bytes actually read ... or an error return code, if the buffer is too
small.
The return code, IMO, should be returned using normal Reg 15
conventions (hope this works for COBOL; if not, a separate
result field for the return code should be provided)
HTH, kind regards
Bernd