AMP will be fine for setting BUFNI or BUFMD, but won't tell VSAM to
look-aside the data buffers. So, without a program product, either
the program needs to establish a LSR pool or use BLSR via JCL to get
look-aside.
I would urge caution in using deferred writes. Just be sure you
understand the implications to your application from lost updates due
to a failure. I have used deferred writes where I have a temporary
VSAM used to hold large arrays where the array is initially empty and
all records deleted before closing the VSAM file.
Michael
At 02:51 PM 5/16/2022, Pommier, Rex wrote:
Thanks, all responders.
Michael, so I'm not stuck in the mid '90s, just the BLSR
documentation is. :-) "First Edition, June 1994"
I have seen the references to BLSR in other documents, like a crypto
manual and some SMP/E references to it, but until I found the 1994
document, I couldn't find anything that actually explained
it. That's where I was getting confused. I'll also need to check
the AMP parm to see if that does the same thing. The DEFERW=YES
option looks interesting (again).
Rex
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On
Behalf Of Michael Oujesky
Sent: Monday, May 16, 2022 2:23 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: [EXTERNAL] Re: IBM BLSR subsystem
PDF -
https://urldefense.com/v3/__http://publibz.boulder.ibm.com/epubs/pdf/iea5j600.pdf__;!!KjMRP1Ixj6eLE0Fj!qkxYWCkBfDGHDC7oenAm5D9KqrxkJrY3t_3JVFdCVrbQCkmMcgu-pyPE7GDVRGTH5pXjbNntD-my9ikgUcff1KGO$
BLSR will help principally if the access is random and the locality
of reference of the data component is good. Otherwise, just
increasing the BUFNI and/or BUFND will suffice. Note that for
sequential access a BUFND of twice the CIs per CA plus two and just
a few BUFNI five or so) usually provides about the best you can get
(incudes over-lapping read I/O to the data component).
I still see BLSR in the 2.5 IEFSSN00 member.
Michael
At 09:36 AM 5/16/2022, Pommier, Rex wrote:
>Hi list,
>
>Is the BLSR subsystem (batch local shared resources) still a
>viable/valuable thing or has it been replaced by something
>bigger/better/faster? I seem to be stuck in the mid-90s because the
>most current documentation I can find on it is from MVS/ESA 5.1 dated
>1994. Is there more current documentation on how to use it and how it
>works? Has it been replaced and deprecated? I just had a developer
>use it last week and experienced a 40+ reduction in I/Os but I wanted
>to read up on its limitations - especially around using it on a shared
>VSAM dataset. However I can't find anything newer
>than 25+ years old. I did multiple internet searches which is
>where I found the ESA manual. I checked the knowledge center and my
>own z/OS 2.2 and 2.4 collections all to no avail.
>
>Thanks,
>
>Rex
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