Wednesday, January 27, 2010

The value of persistence

Persistence has value, especially when we are talking about monitoring and situation alerts. When creating situation alerts, different monitored attributes have different characteristics. When choosing attributes to use for creating situations, keep in mind that some attributes may be more volatile than others.

In other words, some monitored information may be more "spikey". For example, certain resources, such CPU rates, page rates, I/O rates, and DASD MSR times may fluctuate quite a bit during normal workload processing. It's often times useful to monitor, and perhaps alert on these types of items. But, you don't necessarily want to send out a bunch of alerts every time CPU usage or page rate spike up.

That's where the persistence option comes into play. Like in the example I show here, in the situation editor you click on the 'Advanced' button. This will show the persistence option. The default is one interval, but you can click this option to set the persistence option higher. In the example I show a persistence option of 5. What that means is the situation logic has to be true for 5 intervals before the situation will fire. This has the net effect of helping tune out spike alerts, and reducing the occurrence of phony alerts.

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