Mainframe Performance Topics Podcast Episode 28 “The Preview That We Do Anew”

(Originally posted 2 March, 2021.)

It’s unusual for us to publish a podcast episode with a specific deadline in mind. But we thought the z/OS 2.5 Preview announcement was something we could contribute to. So, here we are.

I also wanted to talk about some Open Source projects I’ve been contributing to. So that’s in there.

And it was nice to have Nick on to talk about zCX.

Lengthwise, it’s a “bumper edition”… 🙂

Episode 28 “The Preview That We Do Anew” long show notes.

  • This episode is about several of the z/OS V2.5 new functions, which were recently announced, for both the Mainframe and Performance topics. Our Topics topic is on Martin’s Open Source tool filterCSV.

  • We have a guest for Performance: Nick Matsakis, z/OS Development, IBM Poughkeepsie.

  • Many of the enhancements you’ll see in the z/OS V2.5 Preview were provided on earlier z/OS releases via Continuous Delivery PTFs. The APARs are provided in the announce.

What’s New

Mainframe – Selected z/OS V2.5 enhancements

  • Many of the enhancements you’ll see in the z/OS V2.5 Preview were provided on earlier z/OS releases via Continuous Delivery PTFs. The APARs are provided in the announce.

  • We’ve divided up the Mainframe V2.5 items into two sections: installation and non-installation.

z/OS V2.5 Installation enhancements.

  • IBM will have z/OS installable with z/OSMF, in a portable software instance format!

  • z/OS V2.4 will not be installable with z/OSMF, and z/OS V2.4 driving system requirements remain the same.

  • z/OS V2.5 will be installable via z/OSMF, so that is a big driving system change.

    • However, there is a small window when z/OS V2.4 and z/OS V.5 are concurrently orderable in which z/OS V2.5 will have the same driving system requirements as z/OS V2.4. That overlapping window when z/OS V2.5 is planned to be available via both the old (ISPF CustomPac Dialog) and new (z/OSMF format) is September 2021 through January 2022.

    • After that window, be aware! When z/OS V2.5 is the only z/OS orderable release – at that time, all IBM ServerPac will have to be installed with z/OSMF.

    • All means CICS, Db2, IMS, MQ, and z/OS and all the program products.

    • To be prepared today for this change:

      • Get z/OSMF up and running on their driving system.

      • Learn z/OSMF Software Management (which is very intuitive and try to install a portable software instance from this website.

    • This is a big step forward in the z/OS installation strategy that IBM and all the leading software vendors have been working years on.

      • John Eells came to this very podcast in Episode 9 to talk about it.
    • CICS, Db2, and IMS are already installable with a z/OSMF ServerPac. You can try those out right now.

    • CBPDO will remain an option, instead of ServerPac. But it much harder to install.

      • ServerPac is much easier, and a z/OSMF ServerPac is easiest of all.

z/OS V2.5 Non-installation enhancements.

  • Notification of availability of TCP/IP extended services

    • For many operational tasks and applications that depend on z/OS TCP/IP communication services the current message is insufficient

    • New ENF event intended to enable applications with dependencies on TCP/IP extended services to initialise faster

  • Predictive Failure Analysis (PFA) has more checks

    • For above the bar private storage exhaustion, JES2 resource exhaustion, and performance degradation of key address spaces.
  • Workload Manager (WLM) batch initiator management takes into account availability of zIIP capacity

    • Works most effectively when customer has separate service classes for mostly-zIIP and mostly-GCP jobs

    • Catalog and IDCAMS enhancements

      • Catalog Address Space (CAS) restart functions are enhanced to allow you to change the Master Catalog without IPL

      • IDCAMS DELETE mask takes TEST and EXCLUDE. TEST to see what would be deleted using the mask. EXCLUDE is further filtering – beyond the mask.

      • IDCAMS REPRO moves I/O buffers above line. This will help avoid 878 “Insufficient Virtual Storage” ABENDs.
        We think think this might allow more buffers, and multitasking in one address space.

    • New RMF Concept for CF data gathering

      • There is a a new option, not the default, to optimize CF hardware data collection to one system. Remember SMF 74.4 has two types of data: system specific, and common to all systems.

      • This is designed to reduce overhead on n-1 systems.

  • RMF has been restructured, but all the functions are still intact. z/OS V2.5 RMF is still a priced feature.

    • A new z/OS V2.5 base element called “Data Gatherer” provides basic data gathering and is available to all, whether you’ve bought RMF or not. It will cut some SMF records.

    • There is a new z/OS V2.5 price feature called “Advanced Data Gatherer” which all RMF users are entitled to.

    • Marna is mentioning this, as the restructure has brought about some customization changes you’ll need to do one time for parmlib with APF and linklist.

  • More quite diverse RACF health checks for Pass tickets, subsystem address spaces active, and sysplex configuration.

Performance – z/OS V2.5 zCX enhancements.

  • Our special guest is Nick Matsakis, who is a performance specialist in z/OS Development, and has worked on several components in the BCP (GRS, XCF/XES, …). Martin and Nick have known each other for many years, recalling Nick’s assignment in Hursley, UK.

  • zCX is a base element new in z/OS V2.4, and requires a z14. It allows you to run Docker Container applications that run on Linux on Z on z/OS.

  • zCX is important for co-locating Linux on Z containers with z/OS. You can look at zCX like an appliance, which are z/OS address spaces.

  • Popular use cases can be found here and in the Redbook here. Another helpful source is Ready for the Cloud with IBM zCX.

    • Nick mentions the use cases of adding microservices to existing z/OS applications being served by a zCX container, and the MQ Concentrator for reducing z/OS CPU costs, by running it on zCX. Another is Aspera whcih good for streaming-type workloads.
  • zIIP eligibility enhancements

    • Context switching reduction was delivered to typically expect about 95% offload to zIIP.
  • Memory enhancements

    • Originially it was all 4K fixed pages. New enhancements include support for 1 MB and 2 GB large pages (still fixed) for backing guests.

      • Increases efficiency of memory management, with better performance is expected, mainly based on TLB miss reduction.

      • In house, Nick saw .25% up to about 6-12%, depending on what you are running.

    • Note need to set LFAREA as discussed in Episode 26.

      • LFAREA as of z/OS V2.3 is the maximum number of fixed 1M pages allowed on system. 2GB hasn’t changed.

      • zCX configuration allows you to say which page sizes you’d like to try. Plan for using 2GB.

    • Guest memory is planned to be configured up to 1 TB.

      • zCX uses fixed storage so the practical limit may be lower. The limit used to be much lower, at about 100 GB.

      • Now we support up to 1000 containers in a zCX address space. Capacity is increasing.

  • Another relief is in Disk space limits

    • The number of data and swap disks per appliance is planned to be increased to as many as 245. This is intended to enable a single zCX to address more data at one time.

    • Point is you can run more and larger containers.

  • Instrumentation enhanced

    • Monitor and log zCX resource usage of the root disk, guest memory, swap disk, and data disks in the servers job log.

    • zCX resource shortage z/OS alerts are proactive alerts that are sent to the z/OS system log (SYSLOG) or operations log (OPERLOG) to improve monitoring and automated operations. The server monitors used memory, root disk space, user data disk space, and swap space in the zCX instance periodically and issues messages to the zCX joblog and operator console when the usage rises to 50%, 70%, and 85% utilization. When returning below 50%, an information message is issued

    • But still nothing in SMF to look inside a zCX address space

      • There is Docker-specific instrumentation that can provide that for you.
  • SIMD (or Vector)

    • SIMD is a performance feature, and can be used for analytics.

    • Some containers don’t check if they are running on hardware where SIMD is available.

  • Note that most of what’s in the z/OS 2.5 Preview for zCX is rolled back to z/OS 2.4 with APARs.

  • From this, we can conclude zCX wasn’t a “one and done”.

    • z/OS 2.5 might be a good time to try it. There is a 90-day trial period, as there is a cost for it. But, why wait for 2.5?
  • Nick’s presentation (with Mike Fitzpatrick) can be downloaded here.

Topics – filterCSV and tree manipulation

  • Trees are nodes that have zero to many children. You can have a leaf node (zero children), or a non-leaf node (one or more children).

    • Navigation can be recursive or iterative, which makes it nice for programming.
  • Mindmapping leads to trees. Thinking of z/OS: Sysplex -> System -> Db2 -> Connected CICS leads to trees. Also, in Db2 DDF Analysis Tool we show DDF connections as a tree.

  • Structurally, each node is a data structure with fields such as readable names. Each node has pointers to its children and maybe its parent. This gives it its “topology”, and tree levels.

  • iThoughts is a mind mapping tool, and displays a mind map as a tree. Nodes can have colours and shapes, and many other attributes besides.

    • iThoughts runs on Windows, iOS, iPadOS and macOS.

    • Exports and imports CSV files, with a tree topology and also node attributes, such as shape, colour, text, notes.

    • Has very little automation of its own. But crucially you can mangle the CSV file outside of iThoughts, which is what filterCSV does.

  • filterCSV is a python open source program that manipulates iThoughts CSV files.

    • It could address the automation problem, as it mangling automatically.

    • An example: automatically colours the blobs based on patterns (regular expressions).

      • Colouring CICS regions according to naming conventions
  • fiterCSV started simple, and Martin has kept adding function. Most recently find and replace. As it’s an open source project, contributions are welcomed.

On the blog

So It Goes

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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