From: hobbitt [email protected]
Date: Tue, 1 Feb 2011 15:37:27 -0800 (PST)
Local: Tues, Feb 1 2011 6:37 pm
> If I code a dataset allocation using block size and count, and the ROUND
> keyword:
> (1024,(100),,,ROUND)
> Does the dataset (or at least primary extent) begin on a cylinder boundary?
> The JCL Reference manual (1.12) says that ROUND "requests that space
? allocated to the data set must be equal to an integral number of
> cylinders", which doesn't explicitly say it's on such a boundary.
The JCL User's Guide is more specific on this. It explicitly states:
"if you code ROUND as the last subparameter in the SPACE parameter, the system
allocates the smallest number of cylinders needed to contain the request."
"Cylinder allocation (and therefore ROUND used with average block or average
record) allows faster input/output of sequential data sets than does track
allocation."
"If you request space in terms of average block length, the system will compute
and allocate the smallest number of tracks (or cylinders if ROUND is
specified)"
"if you specify the secondary quantity in cylinders, in blocks, or in records
with the ROUND subparameter, then the secondary space allocated to the data set
starts at the beginning of a cylinder."
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