Paul:
Arthur is correct. If you delete a dataset then ask for the same allocation,
the system will find the best fit which is usually the space you just
deleted so you will get the same space. If you ONLY do an allocation like an
IEFBR14 and do not open it for output, you will not get the eof record,
consequently access methods will read the data just fine assuming blocksize
etc, are correct. The field name in the F1 dscb is DS1LSTAR and is the last
block pointer.
Bill
From: "Arthur T." <[EMAIL PROTECTED]>
Reply-To: IBM Mainframe Discussion List <[email protected]>
To: [email protected]
Subject: Re: ps dataset
Date: Tue, 13 Feb 2007 22:45:42 -0500
On 13 Feb 2007 19:28:48 -0800, in bit.listserv.ibm-main
(Message-ID:<[EMAIL PROTECTED]>)
[EMAIL PROTECTED] (Paul Jodlowski) wrote:
I have a wierd problem, a programmer runs a job that creates a dsn
(tst.report) then he ftp's it down to a server and then uncat/deletes it.
Later on he runs the job again expecting the dsn (tst.report) to be empty.
AND IT SHOULD BE. Well it's not in fact it has the same data as the first
run. I go to 3.4 screen an try to browse the dataset but it says it is
empty. I even ran a IEBGENER and i showed the data???? (of cource we DID
NOT run the uncat/delete step) This is all done on the same volume
(userb4) and it is NOT sms-managed. In fact We don't HAVE any SMS-managed
data sets. We are running of z/os v1r7.
I've hit this, before. This "feature" goes 'way back. I first hit
some variation of it more than 25 years back.
It's caused when the new allocation is in the same exact spot as the
old (deleted) allocation was. This is not rare enough.
Some programs (such as ISPF's 3.4) notice that the VTOC's pointer to
the last record (I forget its name, but it ends with STAR) is zero. No
records means an empty dataset, therefore it won't show any data.
Most other programs (such as IEBGENER) will read until it hits an
EOF.
If you did have this under SMS management, you wouldn't have the
problem. When the system allocates a PS dataset on SMS dasd, it
immediately writes an EOF. You can see recent threads for details on
exactly when this does and doesn't happen.
--
I cannot receive mail at the address this was sent from.
To reply directly, send to ar23hur "at" intergate "dot" com
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