At 09:28 -0700 on 05/25/2013, Charles Mills wrote about Re: Really?
No FTP SITE RLSE?:
For allocating sequential data sets this is the maximum amount of space
that is allocated for the primary extent. If a smaller amount of space is
needed to hold the data being transferred, only the amount actually
needed to hold the data is allocated.
2. What you quoted is very plausible. The quote above does not sound
technically accurate. How would the FTP server "know" the "actually
needed" amount of space to allocate?
The quote can be read two ways.
Way 1 is that the amount you ask for is allocated, the transfer is
done, and then the file allocation is truncated/space is released.
This results in only the needed space remaining allocated.
Way 2 is that your requested space is overridden by the computed
needed space and only that amount is allocated. That is then used to
accept the transfer. To do this the amount of space used for the
source is used to tell how much space to allocate for the target.
That takes into account the LRECL/BLKSIZE of both files as well as
the DEVTYPEs of the devices and the size of the source file.
I think Way 1 is simpler although it can introduce fragmentation of
the target device due to the returned extents. IOW, you ask for 10
cyl (you get cyl 1000-1009) but use only 1 cyl returning 9 cyl (Cyl
1001-1009). Unless Cyl 1010 is free, the next 10 cylinder request
can not be serviced with cyl 1001-1009 thus leading to fragmentation
(assuming the a primary request is serviced by contiguous space not a
group of extents).
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