And better yet, also use a DATACLAS with the Extended attribute so you
are not constrained to only 16 extents per volume.
With Space Constraint Relief. Extended attribute, and Dynamic Volume
Count, both primary and secondary allocations will use as many extents
and volumes as necessary to get the requested primary or secondary space
(not just the 5 extents for primary, 1 for secondary limits of ordinary
sequential dataset allocation), so fragmentation of free space is less
of an issue. Since you are not guaranteed any minimal amount of space
for any individual extent, you also need the larger extent count limit
given by the Extended data set attribute to insure that you are not
artificially restricted by number of extents from allocating available
free space on the assigned volumes.
Using these attributes you can even request a primary allocation that
spans multiple volumes and guarantee that step execution will not even
start if a large minimal primary space is unavailable, but you have to
be careful using this because at least in the past the RELEASE option
would not release allocated but unused space on volumes that contained
no written data, only on the last used volume of the data set (so a
multi-volume primary allocation used for a very small dataset could
consume a large amount of pool space on subsequent unused volumes even
after RELEASE).
Joel C Ewing
On 06/21/2012 03:56 PM, David Betten wrote:
I personally prefer using a volume count of 1 but then setting Space
Constraint Relief to YES with a dynamic volume count. That way my small
files are allocated with 1 volume and additional volumes are only allocated
if needed.
Have a nice day,
Dave Betten
DFSORT Development, Performance Lead
IBM Corporation
email: [email protected]
1-301-240-3809
DFSORT/MVSontheweb at http://www.ibm.com/storage/dfsort/
IBM Mainframe Discussion List <[email protected]> wrote on
06/21/2012 03:24:15 PM:
From: Bill Ashton <[email protected]>
To: [email protected],
Date: 06/21/2012 03:26 PM
Subject: SMS processing setup for secondary extents
Sent by: IBM Mainframe Discussion List <[email protected]>
Hi again, friends!
I have a question that should be simple to answer - I hope - and did not
want to try this and risk losing data until I asked.
I am trying to roll up multiple GDG files created every day into a single
daily file. The files can be either very small or quite large, and so
they
may take one or several extents when complete.
If I have a volume count of 5 in my Dataclas definition, will I be safe
in
that if there is not enough room for a secondary extent on my first
(main)
volume, that it will automatically look on one of the other four to meet
the secondary extent?
I wasn't sure how to test this, and so I hope you can help me!
--
Thank you and best regards,
*Billy Ashton*
...
--
Joel C. Ewing, Bentonville, AR [email protected]
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