On Sat, 6 Oct 2012 13:25:42 -0400, Gerhard Postpischil wrote:
>On 10/6/2012 1:07 PM, Paul Gilmartin wrote:
>> The essence is I'm baffled. I can think of no valid
>> representation in a RECFM=VBS data set of a logical
>> record with zero data length. If I've missed something,
>> please enlighten me. I'd appreciate hex representations
>> if more understandable than English descriptions.
>
>Perhaps I'm missing something, but hex 00040000 defines a null
>record in V, VB, and VBS. VBS runs fine without segment
>descriptor bits.
>
Yup. You're missing something, as I read:
Title: z/OS V1R13 DFSMS Using Data Sets
Document Number: SC26-7410-11
3.1.3.2.2 Segment Descriptor Word
... The first 2 bytes contain the length (LL) of the segment, including the
4 byte SDW.
The length can be from 5 to 32 756 bytes or, ...
...
Figure 76. Segment Control Codes
Binary Code Relative Position of Segment
00 Complete logical record
The diagrams in 3.1.3.2 Spanned Format-VS Records (Sequential Access Method)
appear to allow only SDWs, not RDWs. It may work by happenstance,
but it's documented as invalid.
-- gil
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