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IBM i Navigator System Monitors: Collection Interval

September 08, 2016

Recently I wrote about IBM i 7.3 System Monitor Enhancements and mentioned the default monitor collection interval was changed to 60 seconds.  On the 7.2 release, the default collection interval was 15 seconds; IBM has recently changed the default on 7.2 to 60 seconds.  For this change, you will need the Navigator service pack that was made available this past June.  You can find the details of the required PTFs and PTF Groups on the developerWorks page for Navigator PTFs.

If you create system monitors with small intervals, such as 15 seconds, the monitor collections can become very large, very quickly.  On my small, relatively inactive test partition, system monitors with 15-second collection intervals grow to about 2GB each day.  While monitor collections have a default retention period of just two days, so few GB of storage used by these collections on my small partition was noticeable.  Sixty second collection intervals on my small partition result in monitor collections of around 600Mb.

What if you had created a system monitor on 7.2 that used the default of 15-second intervals?  Or what if you are on 7.3 and decided to create a system monitor with a collection interval smaller than 60 seconds?  In either case, if you want to get back to 60-second intervals, manual steps are required.

Once a system monitor has been started with metrics defined with a small collection interval (that is, less than 60 seconds), system monitor data for that metric type will always be collected at that interval.  The system will automatically make intervals smaller, but it will never automatically make them larger.

There are two steps you must take to change the collection interval to a larger value:
1. Change the system monitor properties to use a larger collection interval.
2. Manually change the system monitor configuration in Collection Services.

Change the System Monitors Properties to Use a Larger Collection Interval

You need change the properties of the system monitors to specify the larger collection interval.  You will need to end the monitor, then edit the properties to change the collection interval.  Be sure to change every metric.  (You could also delete them and create them again).

You might think you can simply reconfigure the system monitors to establish new collection intervals, but this will not work.  Monitor data is collected by Collection Services and the smallest collection interval is remembered; if you end and delete all your system monitors, when you create a new monitor with a larger collection interval, Collection Services will still collect the monitor data at the smaller interval previously used.

Once you have your system monitors configured with the larger collection intervals, you need to modify the Collection Services configuration to change the collection interval used.

Manually Change the System Monitor Configuration in Collection Services

You must modify the collection interval in the Collection Services configuration.  Start by navigating to the Configure Collection Services task. 

On the 7.2 release, you follow Performance --> All Tasks --> Collectors --> Collection Services --> Configure Collection Services.

With 7.3, you simply have to go to Performance --> Configure Collection Services.  (This fast-path navigation will go back to 7.2 later this year.)

Go to the System Monitor Categories tab and then select the “Customize system monitor categories” button.  Now you will see the various monitor categories and their collection frequency.  You can click in the frequency column to change the interval.  You need to change all the categories that have the collection interval too small.

The screen capture below is an example of what this looks like.



Once you have completed these steps, your monitor data will be collected at the intervals configured.

Posted September 08, 2016 | Permalink

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