Mainframe Performance Topics Podcast Episode 24 "Our Wurst Episode"
You’ll have to pardon the pun in our latest podcast episode’s title.
We were also somewhat delayed in getting this out - due to our busy schedules and a few technical gremlins. Hopefully it’s worth the wait.
It’s also quite a long episode so if you listen to it on your commute you’ll have to ask your chauffeur to drive a little more slowly.
Episode 24 “Our Wurst Episode”
Here are the show notes for Episode 24 “Our Wurst Episode”. The show is called this because we both attended the IBM TechU in Berlin, Germany, and our Topics topic is our trip report.
- We have some feedback (again) based on our use of stereo. We now have glorious mono, based on those comments!
- APAR OA55959: NEW FUNCTION - PDUU Support for HTTPS
- AMAPDUPL: Problem Documentation Upload Utility
- How you get a dump to IBM, can be compressed, optionally encrypted, and sectioned into smaller data sets
- HTTPS is important in this because dump can contain sensitive information and FTP is not an acceptable solution for many customers
- FTPS had issues with e.g. firewalls,
- Doesn’t look like this option has been incorporated into z/OSMF Incident Log at this time
- Tailored Fit Pricing for IBM Z
- Enterprise Capacity Solution
- Enterprise Consumption Solution
- Both different from traditional rolling four hour average model
- For Tailored Fit Pricing, all machines must be IBM z14 Models M01-M05 or ZR1, and at IBM z/OS V2.2, or higher
- More information here.
- In Episode 19 Performance topic we talked about Licence-Related Instrumentation.
- Ask MPT
- Danny Naicker asks, “In z/OS 2.4 CSA subpool key 8–15, is it usable for user defined applications?"
- Answer: Prior to z/OS V2.4 User Key Common Storage was available, but it was turned off by default. The downside was no control over who could use it.
- In base V2.4 that specific capability has gone (the old system-wide switch).
- Question probably originates from need to still use User-key CSA because of legacy stuff
- This is where RUCSA (Restricted Use Common Service Area), a new function, comes into play. Allows you to identify applications by using a security definition.
- Usage of RUCSA prior to V2.4 will need APAR OA56180
- RUCSA will be offered in V2.4.
- Thank you to Danny for a good question!
Mainframe Topic: CICS ServerPac in z/OSMF
- IBM’s first delivery on new installation strategy, will be with CICS and associated SREL products. This is the first of many (really, all).
- Choice on new installation strategy or old during ShopZ ordering. Choice is:
- Old is ISPF CustomPac dialogs, or
- New is z/OSMF Software Management and Workflows.
- We encourage making the z/OSMF choice, as that is consistent between IBM and other vendors, and is intended to be easier.
- Infrastructure already available in continuously delivery PTFs, and rolled back to z/OS V2.2. This makes the driving system have the proper infrastructure so anybody can package and deliver that way.
- More details on the z/OS installation strategy:
- Software vendors will package similarly, in a z/OSMF Portable Software Instance,
- Clients will be able to acquire and deploy and configure using z/OSMF.
- z/OSMF Software Management is used to the acquisiting and deployment. (“Deployment” is the new term for “installation”!)
- z/OSMF Workflows is used for configuration. You would see the old ServerPac batch jobs as steps in a Workflow.
- All software that you ordered as a ServerPac, and installed either way, will give you the same (or hopefully better) equivalent installation.
- There is an IBM Statement Of Direction that this installation choice is coming, but we do not have an exact date yet.
- For other software ISVs, they can exploit the new z/OS installation strategy whenever they are ready.
- Prepare now by becoming familiar with z/OSMF Software Management and Workflows
Performance Topic: DB2 And I/O Priority Queuing
- Follow on from Screencast / Blog post topic: Screencast 12 - Get WLM Set Up Right For DB2.
- Recent talk has been about whether to turn off I/O Priority Queuing in WLM.
- Service classes with DB2 subsystems in are heavily I/O Sample oriented, which is unusual among service classes in a system.
- Means access to CPU is not properly managed, as CPU & zIIP samples few, relative to I/O samples. Reminder: Most of DBM1 is now zIIP-eligible.
- Can achieve goal even with lots of delay for zIIP or CPU, but that’s definitely not what you want.
- To see if it is properly managed:
- See if there are lots of CPU / zIIP Delay samples in RMF Workload Activity.
- In Db2 might well see Prefetch etc engines exhausted, which could cause unwanted Sync I/Os and bad SQL performance.
- The effect is just like if there is a real zIIP shortage.
- Instrumentation for DB2 of relevance is Statistics Trace.
- You don’t want to just turn off WLM I/O Priority Queuing, as it’s sysplex-wide, it might affect other work that needs it, and Db2 might actually need it.
- As the name suggests, it gives finer control over I/O priority.
- So, it’s a case of proceeding with caution.
- First you need a reasonably achievable goal for the service class. Make sure you’re more or less achieving the existing goal.
- Second, calculate what the velocity achieved would be without I/O priority queuing .
- Can take out the Using and Delay for I/O sample counts to do this.
- If you don’t do the analysis and act on it a shift to not using I/O Priority Queuing could have unpredictable results.
- You would know that turning off I/O Priority Queuing was helpful by seeing evidence that WLM is managing access to CPU for Db2 better, without hurting other stuff we care about. This evidence would come from RMF Workload Activity Report data.
- On the Db2 side maybe Statistics Trace says Prefetch etc doesn’t get turned off. Or response times get better.
- You should evaluate or adjust the goal attainment, but that is BAU. Changing WLM always needs some care.
Topics: Berlin Trip Report May 20–24
- We both attended IBM Z TechU in Berlin, and got to see each other.
- Marna had about six sessions.
- The SMP/E Rookies session had fabulous attendance - 44. Some were more experienced, but most were not.
- z/OSMF had good attendance too, about 82. More are interested in this topic, especially if you compare to just a couple of years ago.
- Best attended was the z/OS V2.4 Preview, with about 150 people. There was excellent interest in what is coming in the new release.
- Marna got to do a couple of things outside the conference:
- Visiting the Reichstag was fabulous, but make sure to get a reservation.
- Der Dom was also educational, with a walk to the top!
- Marna did her own poster to help with z/OSMF configuration, and several people came by to chat.
- Both Marna and Martin shared a poster about this podcast. We helped with getting one person a podcast app (on each platform), and a subscription to this podcast.
- Martin had five sessions.
- Two were with Anna Shugol, Engine-ering, and zHyperLink.
- One was co-written with Anna, “2 / 4 LPARs”
- Two were solo efforts: Parallel Sysplex Performance Topics, and Even More Fun With DDF
- Martin also took a little time out of the conference
- Each day took a session out to walk in the city.
- It was interesting to wander round former East Berlin.
- The next European IBM Z TechU is in Amsterdam May 25–29, 2020.
- RFE 131187
- zOSMF RESTFILES PUT to remove Windows Carriage Return characters
- Windows files contain a carriage return and line feed and the carriage return character x’0D’ is not being removed. The resulting zOS datasets therefore have a blank line after every data line that shouldn’t be there.
Future conferences where we’ll be
- Both Marna and Martin in SHARE, Pittsburgh, August 5–9, 2019
On the blog
- Martin has several blog posts:
- Marna has one, which the Mainframe topic was based on:
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. So it goes…