Mainframe Performance Topics Podcast Episode 10 “234U”

(Originally posted 2017-02-25.)

So here we are, barely one week on, with another episode. As I indicated, we had bits of this in the can when we put Episode 9 together.

It was really nice to interview Elpida, and we have ideas for a couple more items in a similar vein; I always contemplated this as being the kick off for a stream of stuff.

According to our statistics, quite a few of our listeners are on iOS, so hopefully the Topics topic will give them some ideas (and maybe cost them money). ๐Ÿ™‚

And I’m pleased we’ve got a glimpse of z/OS 2.3, right on cue. ๐Ÿ™‚

And rest assured we have plans for Episode 11, specifically, and beyond.

I had fun with Audacity again, and a couple of minor frustrations with it. I hope you have fun listening.

Below are the show notes.

The series is here.

Episode 10 is here.

Episode 10 “Back In Black” Show Notes

Here are the show notes for Episode 10 “234U”. The show is called “234U” because:

  • We are very happy that we can talk about z/OS V2.3 now that it’s been previewed on February 21, 2017.

  • We liked the consecutiveness 2-3-4, and U added works nicely.

Where we’ve been

Martin has not been anywhere (except for Hursley, UK) since our last podcast.

Marna has not been anywhere, except her desk (to work on SHARE presentations).


Our “Mainframe” topic was a highlight of some of the newly previewed z/OS V2.3 enhancements! We will surely talk a lot about z/OS V2.3 in podcasts to come.

First, it is important to know that z/OS V2.3 will only IPL on an zEC12, zBC12 and higher. Prepare now if you need to.

Here’s a brief list of the items planned for V2.3 (which is planned to GA on September 29, 2017)

  • System logger’s log stream staging datasets can be allocated greater than 4 gigabytes.

  • Data set encryption for z/OS data sets and zFS file systems (policy-enabled), and CF structures (list and cache, with the CFRM policy).

  • zFS:

    • zEDC compression on individual files, and existing and new zFS files systems. Existing zFS while in use!

    • Salvage utility to run online with file system is still mounted

    • Dynamic changes to aggregrate attributes for common MOUNT options, and dynamic changes to sysplex sharing status.

    • New facility (from TSO or UNIX shell) to allow for migration from HFS to zFS, without requiring the “from” file system to be unmounted.

  • email: ability to have an email address in the RACF user profile. JES2 and z/OSMF could use email notification to the user.

  • JES2 JCL, the delimiter keyword (DLM) on SYSIN is extended from 2 to 18 characters long.

  • SCRT is a component delivered in z/OS, with support for enabling ISVs to generate an ISV-unique SCRT report.

  • Auto-starting z/OSMF be default, late in the IPL hopefully after OMVS and TCP/IP are up. The biggest migration action in z/OS V2.3 identified yet.

  • TSO/E support for 8 character userids. Many products require changes to support this, so do planning for this one.

Important SODs:

  • The release after V2.3 is planned to be the last release to support HFS. In other words, the release planned for 2021 is anticipated to not contain HFS support. Move to zFS well before then! Use the new z/OS V2.3 facility to help you with this.

  • In the “future” IBM intends to discontinue delivery of z/OS platform products and service on magnetic tape. DVD remains for physical delivery. We recommended electronic delivery.


Martin had an esteemed guest for our “Performance” topic, Elpida Tzortzatos, Distinquished Engineer from z/OS Development.

Martin and Elpida chatted about several important recent advances made in the area of z/OS memory management.

  • Review of UIC (Unreferenced Interval Count), which is how long in seconds a page has remained unreferenced. High count is low contention, low count is high contention. Since moving to large memory (64-bit, zArch), the design changed to reduce the review frequency from 1 sec to 10 seconds.

    When more memory support was added (128G to 4TB) it was again reduced to not do any UIC updates, other metrics are used to judge contention instead.

    • RMF reports high impact, medium impact, and low impact frames evicted today, for a performance judgement. The calculations are based on a percentage on the page frame table reviewed, which can then be used for a classification of low, medium, or high.

    • Because of today’s behavior with the UIC, other means are more important to use as mechanisms to show memory contraints, such as the AFQ, available frame count. Demand paging is very fast today (with paging from Flash).

    Customers should be looking at average available memory, and minimum too. Make sure your AFQ can handle workload spikes and SVC dumps. Here is a WSC paper about that.

  • Large frames (1MB and 2GB page sizes): the Dynamic Address Translation (DAT) is on the critical performance path for every program execution. The TLB (Translation Lookaside Buffer) is close to the processor chip(expensive and not a lot of memory). The TLB size hasn’t changed much, but addresses that can be covered is increased with large frames. To improve performance, then increase the size of the working set in the TLB, to reduce a TLB miss.

    Use the LFAREA specification for 1MB and 2GB frame usage. Breaking of 1MB frames into 4K (and reconsolidation) can be done, but not in all cases.


  1. Memory management has evolved to scale to nicely support very large sizes.
  2. Memory is interesting, and has been scaling up and improving performance with each release, and done it in a way that improves application performance.


Our podcast “Topics” this time was about Automation in iOS, and should appeal to anyone looking at getting more use out their Apple products. Martin talked about how to save time with tailored apps from simple ones, and ways of automating for “bulk” processing.

A wide range of topics to do with iOS and Web Automation were covered in the Topics topic.

The iOS apps mentioned were

One that wasn’t mentioned but which would be useful is:

The x-callback-url specification is described here..

The web automation services discussed can be found here:

Mostly everything discussed in this item is from 3rd party app developers. Although not everything has an Android equivalent, we can see where this is going and how to easily take advantage of what you have once you know about it. It’s advanced quickly over the past few years.

Customer Requirements

Marna talked about one customer requirement that caught her eye, and even Martin liked:

The requestor would like BCPii to provide more CEC information, specifically:

  • storage-total-installed

  • storage-hardware-system-area

  • storage-customer

  • storage-customer-central

  • storage-customer-available

Where We’ll Be

Marna will be at SHARE in San Jose, California March 6 through March 10, 2017.

Martin has a plan to go nowhere but that could be oh so easily derailed. ๐Ÿ™‚

On The Blog

Martin has published one blog post recently:

Marna has written one:

Contacting Us

You can reach Marna on Twitter as mwalle and by email.

You can reach Martin on Twitter as martinpacker and by email.

Or you can leave a comment below.

Published by Martin Packer

I'm a mainframe performance guy and have been for the past 35 years. But I play with lots of other technologies as well.

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