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View Memory Pools and Faulting With the Performance Data Investigator

November 11, 2013

Recently I wrote the blog Work with System Status - the Navigator Way, which described how, using Navigator for i, you can make some simple customizations to get the Active Memory Pools view to show you additional information – pool sizes, fault rates, etc., and mentioned that the work management tasks link to the performance tasks.

This week, I want to expand upon the performance tasks side of this – and share with you some relatively recent enhancements in the Performance Data Investigator (PDI) that provide graphs of your memory information.

For the features I review in this blog article, the underlying data is provided by Collection Services, which you should be running all the time. The capability to view Collection Services data with the PDI is included with the operating system, so all of you have the capability to view these charts. You just need to make sure you have the latest Navigator for i PTFs.

Using the Performance Data Investigator, you can see memory and faulting information. It’s easiest to explain this with a few examples.

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Once you are in the Investigate Data task, expand Collection Services, and you will find several folders – the ones of interest for this discussion are the Memory folder and the Page Faults folder. Each contains a set of perspectives (charts). The Page Faults perspectives have been there for a long time. The Memory perspectives are relatively new.

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If you expand the Memory folder, you will discover the following perspectives:

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Hmmm … this sure looks a lot like what we see on WRKSYSSTS, doesn’t it? It is … and it can be a bit better, particularly if you want to see the information over time. With WRKSYSSTS, you see the real-time values; if you want to take note of how they are changing, you either need to take screen captures or write down the values. But Collection Services collects this data on an ongoing basis and PDI allows you to visualize that data so you can see what has been happening over time. That might be very valuable in understanding what is happening on your partition. (Note: the granularity of what you see with PDI and Collection Services data will depend upon the collection interval you have configured.)

Below is an example view of the Memory Pools Sizes and Fault Rates perspective; on my partition, the performance adjuster (QPFRADJ) system value is on.

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From this perspective, there are several drill-down options. One option is to drill down to “Page Faults By Job or Task”, where you identify what jobs were faulting. From this perspective, you can then drill into the page faults for one job to see that specific job’s behavior.

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Below is another example screen capture, this one being “Memory Pool Activity Levels”. In this example, a workload started to ramp up around midnight and the work continued to increase and we can see this represented in our activity levels. (This was a stress-test workload done in the Rochester lab.) Performance adjuster was on.

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If you expand the Page Faults folder, you will find more perspectives for viewing faulting data:

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These are just a few simple examples of some of the perspectives you can view. Take the time to look at your Collection Services data with the Performance Data Investigator – you’ll likely learn a lot about what is happening on your system.

If you are not familiar with the Performance Data Investigator, the article I referenced earlier is a good place to start. There are also many additional resources on the IBM i performance tools page Resources page on developerWorks.

To learn about the new features that have been added to PDI, refer to the Performance on the Web documentation on developerWorks. The memory perspectives were part of the Spring 2013 update.

 

 

 

Posted November 11, 2013| Permalink

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