I am talking about classic MVS datasets all the time;
not sure about USS files.
With classic MVS datasets (RECFM=FB), the C runtime supports large blocks
even with short record lengths. That is, if you do fopen ("dd:outfile",
"wa"),
a file allocated to OUTFILE which has some records already (in a block
which
is not filled up completely) will be filled before the next empty block
is allocated.
At least, this is my understanding, and everything else would be a shock
for me.
There should be no difference in behaviour (in principle), no matter if you
are writing to a classic MVS dataset or to a USS file.
Kind regards
Bernd
Am 19.06.2022 um 19:36 schrieb Seymour J Metz:
Does Unix System Services support RECFM=FBS? If it does, then fopen needs to
properly handle short blocks for append.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
________________________________________
From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of
Bernd Oppolzer [bernd.oppol...@t-online.de]
Sent: Saturday, June 18, 2022 3:31 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Some UNIX file usage questions
I am very sure that if you issue fopen (with "append")
on a file with, say, LRECL = 24 and BLKSIZE = 9600, which has
one record and one block with only one record in it,
and you write a second record, that then this file will still have
one block, but now two records.
At least this is what I expect from the C runtime.
Kind regards
Bernd
Am 18.06.2022 um 21:23 schrieb Steve Smith:
QSAM to a traditional PS file with the process you described is certainly
going to write only short blocks. Given the amount of data involved, would
it matter?
However, besides USS files, you could consider an ESDS. VSAM maintains its
CISIZE and blocksize quite rigorously. And it should be very safe.
sas
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