On Tue, 11 Jun 2013 09:01:16 -0500, Tom Marchant wrote:
>
>Clearly, if a record ends, for example, three bytes short of BLKSIZE,
>another record cannot be added to that block. The block would
>have to be written as is, with a block size of three bytes less than
>BLKSIZE or a program reading it might have errors.
>
An alternative is to supply a null segment. "Data Management" seemed
to imply even a null segment must be at least 4 bytes. I can infer no
such restriction from "Using Data Sets".
What's the motivation for null segments? Who uses them? I can imagine
using them to deal with the 18-byte minimum on tapes. (Hmm... How
does RECFM=VB, or even RECFM=FB,LRECL<=17 deal with the hazard
of a block <17 bytes as the last block in a data set?)
In:
• z/OS V1R13.0 DFSMS Using Data Sets
• SC26-7410-11
I read:
3.1.3.2.4 Null Segments
... (You do not have to be concerned about null segments unless you have
created a data set using null segments.)
What if someone else, not I, created the data set using null segments?
Needn't I likewise be concerned?
-- gil
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