Syncsort's MFX sort when using the Global Sort Monitor measures systems
resources, both on an instantaneous basis and on a historical basis to judge
how much memory each sort should use. If you give a MFX sort a REGION=0M it
may use 8M or 1.5G depending on what the current memory demands are by other
processes, and what the historical data indicates will be needed over the life
of the sort. MFX automatically does all that for you.
If you have a 10G machine and over 2G of it are free, who cares that a sort
comes along and uses a gig. It isn't hurting anything. On the other hand if
there is paging already happening, you only want the sort to take as much as is
absolutely necessary to do the job with relative efficiency.
Chris Blaicher
Technical Architect
Mainframe Development
P: 201-930-8234 | M: 512-627-3803
E: cblaic...@syncsort.com
Syncsort Incorporated
2 Blue Hill Plaza #1563
Pearl River, NY 10965
www.syncsort.com
Data quality leader Trillium Software is now a part of Syncsort.
-Original Message-
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf
Of Farley, Peter x23353
Sent: Monday, October 2, 2017 12:49 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Sort Question
> -Original Message-
> From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU]
> On Behalf Of Paul Gilmartin
> Sent: Monday, October 02, 2017 12:24 PM
> To: IBM-MAIN@LISTSERV.UA.EDU
> Subject: Re: Sort Question
>
> On 2017-10-02, at 09:29, Farley, Peter x23353 wrote:
>
> > With respect to the REGION size, remember that SORT (both IBM and its
> > competitors) is most efficient the more memory you can let him have. I
> > have found this especially true for COBOL-based SORT's.
> >
> But does this contend adversely with concurrent jobs?
IMHO it is the job of the Capacity and Performance team to tell the application
programming teams when application jobs are contending for memory and causing
paging, especially if it causes SLA's to be missed or near-missed.
> > Consider using a region of at least 500M for large-volume sorts, and be
> > sure to tell SORT he can use (most of) it via the SORT parameters. The
> > more memory he has available the fewer SORTWK's and SORTWK I/O's he will
> > need to use.
> >
> REGION=0K?
Only if allowed by IEFUSI. Many large shops do not allow it except with
special dispensation and approval, specifically because of the issue you raised
above about memory contention.
> > Also "buffer up" all of your high-volume input files with high BUFNO (QSAM)
> > or AMP='BUFND=,BUFNI=,RMODE31=ALL' (VSAM) parameters (as
> > appropriate). Consider using SUBSYS=BLSR or SMB parameters for high-volume
> > VSAM inputs as well.
> >
> I would hope (wish) that DFSORT would supply optimum defaults. But can an
> application discern in OPEN exit whether the options were supplied in JCL or
> as OS defaults?
>
> Does DFSORT rely on QSAM or on idiosyncratic EXCP? I'd expect that in the
> era of oscillating merge it relied on EXCP.
Of course SORT uses his own EXCP (or OCO media manager interfaces) where
possible, as it is far more efficient than QSAM. I was referring to the OP's
original COBOL source for this SORT question. My reply concerned
application-read input files, not directly-read-by-SORT files. For JCL sorts I
always let SORT decide how to optimize his files, but COBOL SORT's act as E15
and/or E35 exits, so COBOL I/O can and often is being used for those I/O's,
whether directly for the file to be sorted or a multiplicity of inputs used to
construct the SORT input and output records.
> > Memory is (relatively) inexpensive, so use it to your advantage. Your
> > SLA's will appreciate it.
Peter
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