On 12/8/2013 8:58 AM, Jon Perryman wrote:
With the exception of DISP=MOD with multiple open/writes and that the last
block will always be, I don't see the difference between FB and FBS. How would
FB create a short block in the middle?
Well, except for DISP=MOD, it won't: it is a DSIP=MOD situation
that allows the possibility.
-Steve Comstock
Jon Perryman
----- Original Message -----
From: "[email protected]" <[email protected]>
To: [email protected]
Cc:
Sent: Saturday, December 7, 2013 10:55 PM
Subject: Re: Something to Think About - Optimal PDS Blocking
Yes, however FBS stands for Fixed Block Standard, not Spanned.
Exactly. And the last record in an FBS data set can be "short", i.e.
less than lrecl. The short record denotes the end of the data set. And all the
utility programs know it and stop processing once they reach the short record.
That is all fine and well as long as we are not dealing with a multivolume data
set.
Think standalone dump written striped to - say - 5 volumes. Each volume has a
data set in format FBS, but only one of the volumes can have a short record.
SAdump knows that, and IPCS knows it, too. The utilities don't. So assume
that you took a complete sadump to 5 volumes and the sort record happens to be
on the first volume. Then you use a utility (ICEGENER is my favourite) to copy
somewhere else. You end up with a severely truncated sadump. One fifth, to be
exact. IPCS will read the truncated dump to the best of its abilities, but you
will get all kinds of 'storage not available' warnings when looking at
the dump.
Last time a customer sent me an sadump, it had 27000cyl. I got all kinds of
warnings and got lucky in that the sadump messages were clearly truncated and
didn't show the 'successfully finished' message. It turned out that
the wrong utility was used for copying, and the actual dump had 63000 cyls.
Visible when IPCS COPYDUMP was used for copying. IPCS knows that a striped
sadump can have the short record "earlier".
Barbara
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