Welcome to the new look of Cheryl’s List! We will still be providing the same valuable content that you know and love, but with a slightly fresher look.
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We published the latest Tuning Letter last Thursday, so this Cheryl’s List is just a summary of the topics we covered in this latest issue. If your company has a subscription to the Tuning Letter, make sure that you get a copy of the latest 136-page issue. If you are not sure whether your company has a subscription or not, feel free to contact us and we will check and let you know. And if you don’t have a subscription, consider joining our happy family of readers, some of whom have been with us for over 25 years. You can get more information here.
Our next Cheryl’s List will be out soon, with any updates to the Tuning Letter, latest tips, and some suggestions about must-see sessions at the upcoming SHARE in San Antonio. Cheryl and I will be there, presenting two sessions, so please drop by and say hello if you are at the conference.
Management Summary from Tuning Letter 2015 No. 4
The 136-page 2015 No. 4 Tuning Letter was emailed to paid subscribers on February 4, 2015. This is the second issue produced using FrameMaker. We did some fine tuning since the last issue and hope that you will find this one even easier to use. However, just like system tuning, tweaking the Tuning Letter is a never-ending process, so please let us know what else we can do to make it even more valuable to you.
The following is our Management Summary from that issue, talking about just some of the contents of that Tuning Letter:
z/OS 2.2 Features
z/OS 2.2, released at the end of last September, delivers a wealth of new features. A subset of them are also available for 2.1 and even z/OS 1.13 for some of those. We listed those enhancements in ‘z/OS 2.2 Changes Available in Previous Releases’ in Tuning Letter 2015 No. 3.
Cheryl and I were discussing how to handle all the other features. We could have just listed them all, but you can easily find that information elsewhere. Instead, we felt that an article providing a little more detail on the top 15 features would be more valuable. So we pored over the announcement letters, Redbooks, Hot Topics articles, SHARE presentations, and many websites and articles, and came up with the list described in the ‘What’s New in 2.2 (Part 2)’ article. We are confident that every one of our readers will find at least 2 or 3 enhancements that will bring value to their company.
IBM introduced HiperDispatch on the z10 generation of CPCs. With each new CPC generation, it became more powerful and became integral to delivering the maximum capacity and optimizing that model’s architecture.
With z13, HiperDispatch takes another leap forward. Due to its new internal structure, the variability on a z13 is higher than on previous generations, with some workloads getting spectacular results, while others were not as well suited. Effective use of HiperDispatch is an important part of making sure that you are getting the most out of your z13.
However, from conversations with our customers, conference attendees, students, and IBMers, we know that many mainframe technicians are not as familiar with HiperDispatch as they would like to be. So, Alain Maneville and his colleague Maxime Rochemir, both from IBM France, kindly agreed to work with us to create an article designed to help plug the gaps in your knowledge of HiperDispatch. Whether you are involved in capacity planning, or day to day system performance, you should read the ‘HiperDispatch Questions and Answers’ article.
Holistic Capacity Planning
Conventional wisdom has it, that to get the maximum value out of your mainframe, you need to be running it as close to 100% busy as possible. Certainly, that is the mindset that I grew up with. And it is compounded by the fact that you can run a z/OS system at close to 100% utilization and still meet your Service Level Objectives.
However, with dropping hardware prices, and increasing software costs, the time has come to step back and objectively examine whether that is really the most cost-effective way to run a mainframe.
We were very fortunate to receive an offer from one of our long-time customers, Todd Havekost in USAA (the 5th largest car and homeowners insurance company in the United States), to tell us about their experiences in exactly this area. By increasing the capacity, and decreasing the utilization, of their z13s, they were able to reduce their peak MIPS utilization by over 9000. We will leave it to you to calculate what a 9000 MIPS reduction would do to your software bills.
This article is compelling reading for anyone interested in controlling the total cost of ownership of your mainframes. USAA’s experience really turns mainframe capacity planning and management on its head. Whether you have a z13 or an older processor, or whether you plan on upgrading in the near future or not, ‘A Holistic Approach to Capacity Planning’ is an article that everyone responsible for mainframe capacity planning should read.
One of the most popular of our regular articles is our User Experiences section. What good business person doesn’t relish the opportunity to learn from the experiences, positive and otherwise, of their peers. In this issue we cover news about XCF couple data sets and disk mirroring, HiperDispatch and group capping, SMF user records, and JES3 to JES2 migration. See the ‘User Experiences’ article for more information. And please encourage your colleagues to send us their experiences. Just as we all benefit from the experiences of others, we also all have experiences of our own that would be helpful to others.
VSAM RLS Setup for Performance
This is the latest installment in Roy Farren’s series about VSAM RLS. Compared to DB2 and IMS, there is very little guidance in the public domain about the optimal way to configure your VSAM RLS environment. In this article, Roy describes the system and SMS parameters that define the buffers and Coupling Facility resources that will be available for VSAM RLS use, and shows how to associate data sets and SMS service classes with those resources. Compared to DB2 and IMS, there is relatively little up-to-date documentation on this topic. Roy and I worked with IBM’s Terri Menendez and Neal Bohling to ensure that our guidance reflects the product’s latest capabilities and their best advice based on their experience with VSAM RLS customers around the world.
Even if you already have VSAM RLS up and running, we recommend that you read ‘VSAM RLS – Configuring for Performance’ and compare our recommended setup to yours – you might find some opportunities for further optimization. Our next issue will provide advice about monitoring and tuning your VSAM RLS configuration to ensure that it remains at peak performance.
zPDT Performance and Capacity
As z/OS installations look for ways to control costs and increase the productivity of their application developers, there is growing interest in the zPDT-based Rational Development and Test for z/OS (RD&T) product. RD&T is attractive because of its flexibility, the fact that it is specifically tailored for application development, and the opportunity it provides to reduce development costs by moving to Intel-based hardware.
However, one challenge that installations face, especially the larger ones, is sizing the hardware for RD&T. Based on the mainframe tradition of sizing CPUs based on MIPS, they expect a similar mechanism for RD&T. Sadly, the vast array of PC hardware options makes it nearly impossible to have a single capacity metric for zPDT. This truly is an ‘it depends’ type of situation.
To try to help potential RD&T customers and resellers, Bill Ogden and I have been doing some informal performance testing and we provide our findings in ‘zPDT Performance and Capacity’. While this is far from comprehensive, it does provide a description of the considerations for zPDT RD&T performance. Future issues will provide updates as we expand our testing to more configurations and we delve into more tuning options.
Feeling overwhelmed with the volume of information and infomercials that come your way every day? We know the feeling. For you, this is vital information, but only a tiny part of your long list of responsibilities. For us, this is our job. So take advantage of all the research we do to identify critical fixes and new functions, possible performance issues and opportunities for savings, along with a summary of recent Techdocs, Redbooks, blog postings by industry leaders, and information about upcoming conferences. We read thousands of pages of information and boil them down so that you can cherry pick just the ones that you really need.
That’s all for this Cheryl’s List. Don’t forget that we love to hear from our readers, so if you have any interesting (or harrowing!) experiences, or any good Irish jokes, please let us know. You can contact us on email@example.com.
Editor, Cheryl Watson’s Tuning Letter
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