On Wed, 8 Aug 2012 14:06:04 +0200, R.S. wrote:
>
> .... BTW: your allocation request was
> illogical - you wanted to have 80-byte records and requested 1 byte.
> Such request has to be re-interpreted or canceled. ;-)
>
As in:
DD LRECL=80,SPACE=(1,...),...
Seveal contributors argued that there was no way a 1-byte block
could be written if LRECL=80, and the construct should result in
an error.
The JCL RM says:
blklgth -- (only if AVGREC is not coded)
Specifies the average block length of the data, in bytes.
The blklgth is a decimal number from 0 through 65535.
Really!? In fact by experiment, in JCL:
DD SPACE=(0,1),...
and in TSO
ALLOCATE AVBLOCK(0) ...
are both accepted without complaint. I suppose allocation adds a
count and an IBG; divides track size by that; takes the ceiling and
requests the resulting number of tracks (almost certainly 1). I have
little problem with that. I haven't investigated whether SPACE=(0,99999)
allocates fewer tracks than SPACE=(1,99999). It's possible that integer
arithmetic or 32-byte chunking gives the same result for both.
Perhaps I'll start coding SPACE=(0,1) in JCL to allocate minimal
data sets, just to startle readers.
-- gil
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