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Status Delivered
Workspace IMS System Services
Categories General System
Created by Guest
Created on Sep 17, 2020

RELATED IDEAS

enhanced IMS default DFSSPMxx for HIOP

Performance analysis of IMS pool usage by STRG trace and dump of controlregion reveals that
requested HIOP buffersizes X'10000' and x'8148' for QCF are larger than largest buffersize in DFSSPMxx default for HIOP: 32768 decimal (see IMS system definition reference). IMS documentation (IMS redbook SG24-7324-00 page 134) strongly recommmends to avoid oversized buffer usage. The reason is that getmain/freemain needs to acquire the z/OS LOCAL lock.
IMS should *by default* allocate some 64k HIOP primary buffers for QCF(and others) usage at startup. The performance benefit of getmain avoidance outweighs the storage consumption, for example 5*64k= 320k in extended private nowadays is not a big deal. IMS queues typically occur when there are already performance problems on the LPAR, an addon penality getmain is counterproductive.
We have opened case 4196908 with IBM to get the IMS defaults for DFSSPMxx enhanced. IBM came up with the recommendation to request an QCF doc change that points to the needs of having a dedicated DFSSPMxx member . We don't think this is the way to go.
We appreciate to do it once for all customers in IMS code instead of letting every customer re-discover this performance issue again and fix it by themselves by defining an dedicated DFSSPMxx
FPL=HIOP,(256,64,32,N),(512,64,32,N),(1024,32,16,N)
FPL=HIOP,(2048,32,16,N),(4096,16,8,N),(8192,8,4,N)
FPL=HIOP,(16K,4,2,N),(32K,4,2,N),(64K,4,2,Y)
with
grabbing HIOP defaults from IMS SD manual
adding 9th (maximal 32 allowed,see macro DFSPOOL and IMS SD manual) buffersize 64k(allowed maximum) with allocation at startup.

Idea priority Medium
  • Guest
    Reply
    |     Apr 5, 2021

    This functionality was delivered in IMS version 15 APAR PH30072.

  • Guest
    Reply
    |     Sep 30, 2020

    Hi,

    Thank you for your interest in keeping IMS a vital and successful product. Software development has continuously evolved during IMS’s lifetime, and so has IMS itself. We have kept pace with, adopted, and implemented many industry standard best practices within our organization, including Continuous Delivery, Design Thinking, and Agile.

    When choosing new features to add from the list of requirements in our backlog, we assess which will bring the most value to as many clients as possible and prioritize those.

    After reviewing this request for enhancement and assessing its potential value, our decision is to open an APAR to address this issue. The APAR we have created in PH30072. We believe this is a more appropriate action for this item given the details provided.

    Have a great day!

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