Thanks Greg for the useful comments. 

The target platform is initially another HP3K, but eventually will 
mostly likely become an HP-UX server once we start to migrate our systems. 
Yes, FTP is called from our cobol programs, but all 
we've done is package up a call to the HP3K's FTP client inside
a general subroutine which creates the necessary scripts for us. I could
do the same for the compression routine - calling whatever I needed via
a subroutine of our creation, but I was hoping that there was some way
of directly invoking the compressing from our Cobol programs - i.e. some
sort of system instrinsic call I could make. 

The data will (eventually) be all plain ascii text, so there is no little endian problem. 

>>> "Greg Stigers" <[log in to unmask]> 28/08/03 16:46:54 >>>
"Tony Summers" wrote in part:
>Anybody any thoughts on the best way to compress a
>variable record length file from a Cobol program
>prior to transmitting it via FTP ?
Sure, but there are plenty of questions. What is the target platform? That
will likely constrain your list of choices. You will need a compression
scheme available on both sides of this ftp. LZW is available on various
platforms; I've used it on NT. STD may be a good choice if the target is
another 3000. You go on to mention bytestream, which makes me suspect that
you are going to someone else's HFS. Zip and tar formats can work,
particularly with bytestream if the target requires it.

How fat is the pipe across which you will ftp this file? There may be little
actual time savings by compressing, if the pipe is fat. Appropriate
benchmarking will answer this. Years ago, I found that I could cut total
wall time in half by compressing, sending, and decompressing, versus sending
uncompressed over frame relay across a WAN. Although since my ftp ran at
night, I had less concern about network congestions, and playing well with
others. Your mileage will vary.

>I could invoke Zip from within the program and unzip it
>after it has been FTP'ed, but there's probably a simpler way.
Is this ftp being controlled by a COBOL program? If so, then I understand
you to mean calling a compression program from COBOL as well. If not, then I
assume you want to script the compression logic. It may be worth mentioning,
since the data is coming from a COBOL program, and if you are using binary
or packed decimal fields, that you have to concern yourself with whether the
target platform is big endian or little endian, although that has nothing to
do with the compression method chosen.

Greg Stigers
this space for rent



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