Monday, April 2, 2012

​ "Granularity"- An Important Factor in test result Analysis

You can make the graphs easier to read and analyze by changing the granularity (scale) of the x-axis. The maximum granularity is half of the graph's time range. To ensure readability and clarity, Analysis automatically adjusts the minimum granularity of graphs with ranges of 500 seconds or more.
The granularity affects the graph smoothing, or number of data points. A high granularity value will reduce clutter and improve readability, but it may hide events such as spikes. The trick is to adjust the granularity to maximize readability but accurately represent any important events.
Following example shows the average transaction response time graph with three different granularity.

Granularity=128 Sec

Granularity= 64 Sec

Granularity=16 Sec

It can be seen that reducing granularity gives more accurate test results and shows if the result has frequent spikes and response is not consistent.
SO it’s really important that we choose right granularity while analyzing test results nad preparing test reports and graphs.
Note:
  • However for larger performance tests setting the granularity too low may cause the Analysis tool to hang for a few minutes.
  • It is also important to note that Analysis recalculates the average response times when the granularity is changed, so be sure to always use the same granularity when comparing test runs.

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