Doug, this raises a good point. If I have a COBOL program doing a SORT
in the middle of the program (I am not sure if the big file is doing
this, too or not), is using this DFSPARM the best way to force the use
of 15 Dynalloc SORTWK files, so I would not have to code SORTWK DD
statements?
Thank you and best regards,
Billy Ashton
------ Original Message ------
From "Doug" <dsh...@bellsouth.net>
To IBM-MAIN@listserv.ua.edu
Date 7/3/2023 2:45:28 PM
Subject Re: SORTWK space usage
Try adding this instead off sorted dd.
//DFSPARM DD *
OPTION DYNALLOC=(SYSDA,15),DYNSPC=768
/*
You can add other options too.
Regards, Doug
On Jul 3, 2023, at 14:34, Michael Oujesky <reflect...@oujesky.net> wrote:
Just a warning, but the SORTWK specification decision depends on how SORT is
provided the input data. If via SORTIN, then allowing SORT to make the
determination should be fine. But when the incoming records are provided SORT
one records at a time (piping, E15 exit, etc,) then nudging SORT's SORTWK
decision by providing some SORTWK areas would probably be a better approach.
At 01:13 PM 7/3/2023, Billy Ashton wrote:
Thanks everyone - these are good recommendations.
However, the guy who came to me first has a job that sorts 450 million records
of 110 bytes, and I can't see how I could run SORT without specifying SORTWK DD
statements. Are there special configuration options I can verify that we have
in place to help my comfort level that I could eliminate SORTWK DD?
If the programming team are not convinced, does this look right, based on the
discussion - and based on a 100% Disk sort, which is not likely?
450mill * 110 * 1.5 = 74250000000 = 69GB
so maybe SORTWK01 - SORTWK10
//SORTWK01 DD UNIT=WORK,DSNTYPE=LARGE,SPACE=(CYL,(4000,1000))
to
//SORTWK10 DD UNIT=WORK,DSNTYPE=LARGE,SPACE=(CYL,(4000,1000))
and this will give me 4000 + (15*1000) on each, or 40000c primary + (up to 150
* 1000) secondary
While we have been talking here, I have looked, and found some jobs with
//SORTWK01 DD UNIT=(WORK,5)...
and this will not work, is that right, Sri Kolusu? I would only get the first
volume anyway?
Thank you and best regards,
Billy Ashton
------ Original Message ------
From "Farley, Peter" <0000031df298a9da-dmarc-requ...@listserv.ua.edu>
To IBM-MAIN@listserv.ua.edu
Date 7/3/2023 12:44:43 PM
Subject Re: SORTWK space usage
I will add on to Sri's excellent answer with my very STRONG recommendation NOT
to use hard-coded SORTWK's in your JCL. Both of the major SORT vendors (IBM
and Syncsort) do a far, far better job of estimating necessary SORTWK space and
memory utilization than any human could hope to do.
I also STRONGLY recommend that you give your JCL and program-controlled SORT
steps as much memory in the REGION parameter as your installation allows for
production and test jobs. Both of the major SORT programs will figure out how
much of that memory to use, whether and how much of it to use in the current
WLM environment, and will make VERY effective use of as much of it as they can
to cut down on SORT execution and elapsed time. Memory is (relatively) cheap,
don't be afraid to use all you've got available to shorten your SORT times.
My basic advice is don't try to second-guess these very intelligent programs -
they each have more than half a century of practice and experience that none of
us can match, even those of us who have been around that long.
Peter
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Sri h Kolusu
Sent: Monday, July 3, 2023 12:28 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: SORTWK space usage
I will only get the primary space of 5000 cylinders, and the other 14x2000
cylinders is never used. Is that right?
Billy,
No. Incorrect. DFSORT will make use of BOTH primary and secondary space
allocations ( 1 primary + 15 Secondary) for a total of 16 extents. So if you
allocated 1 sortwk dataset with (CYL,(5000,2000)), then DFSORT would use 5000 +
15* 2000 = 5000 + 30000 = 35,000 cylinders. Also note that the secondary
extents will only come into picture ONLY when needed.
Is there a written explanation I can forward to the programmers so they
understand this?
Also (since I know it will come), is there any good way to calculate how much
DASD sortwork would be used? I know this depends on what is in memory at the
time, but want to get a better handle on how Sort determines what it needs.
I would suggest that you use DFSORT's Dynamic Allocation as it will allocate
the required workspace optimally rather than programmers calculating it. The
reason is you don't want to change the allocation every time there is an
increase/decrease in the number of records to be sorted.
Having said that, here is a general formula that you want to use.
The amount of sortwk space required depends on the size of the file. It
usually ranges from 1.3X to 1.8X of the size of the file to be sorted depending
on the sorting path that DFSORT chose.
Filesize = Number of records * Avg length of the record ( for Fixed length
RECFM=F or FB , it is the LRECL value, or RECFM=V or RECFM=VB is the average
length of the record)
However, that range is applicable ONLY when the entire file is being sorted
using Disk workspace. DFSORT has the capability of using memory (real and
auxiliary storage) and if it runs out of it, it will then use disk workspace.
Thanks,
Kolusu
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