Differential Analysis lets you monitor changes in the performance and the stability of your applications.
Differential Analysis automatically identifies important changes in the performance of your applications. Legacy baselining predicts what is normal. Differential Analysis tracks the stability of your applications. It looks for uncontrolled variance in the Average Response Time of your frontend, backend, and business transaction metrics. The results are not very different from how a seismometer displays earthquakes. Uncontrolled variance appears as dark areas in an otherwise stable white strip, letting you pick out periods of instability across minutes, hours, or days -- even for hundreds of applications.
The core of Differential Analysis was invented and put into practical use by Walter Shewhart to address the problem of quality control on buried telephone lines. Shewhart invented statistical control charts and the Western Electric Rules. Western Electric Rules are decision rules that detect out-of-control variance on control charts.
The Differential Analysis map is a visual exploration of the stability and responsiveness of many applications: dozens, hundreds, or even thousands of them. Each strip in the map corresponds to a single metric, for example, the Average Response Time for a specific frontend application. In a quiet, stable period the strip is a light shade. When instability occurs, the shade of the strip darkens progressively according to the severity of the instability. Thus, a single strip lets you see the stability of a single application or business transaction over time. The map sorts the most unstable strips to the top and makes it easy to scan through dozens of applications for unstable response times.
Variance intensity determines the color of the strip at a point in time. It is represented as follows:
Gray -- total inactivity, the application received no transactions over the interval measured.
Differential Analysis also reports peak instability over an interval of lower instability (a lighter shade). In this case, the strip shows the shade of the overall stability as usual. When the maximum variance intensity is greater than the average variance intensity for a period, a vertical line appears in the cell. The line is the shade of the maximum state. This depiction helps to ensure that you do not miss an important period of instability while looking at a longer time range. For example, during a long interval, any instability at shorter intervals can be averaged out. The map cell is striped with a vertical line indicating the peak variance, so that an important period of instability is not missed.
Be aware of the following special cases:
APM includes a data point limit clamp that limits all query results beyond a specified number:
Clamps the maximum number of data points that the Enterprise Manager retrieves from the SmartStor disk during a batch of metric queries.
Clamps the number of data points that are returned from a batch of metric queries.
Important! If you use the data point limit clamps, you receive incomplete results in the Differential Analysis maps when the data point limit clamps are reached. Use the Differential Analysis intelligent clamping, and turn on data point limit clamps only when necessary.
Real-time performance data displays in the Differential Analysis map. This map shows a baseline summary of the actual values, the prediction, and the standard deviation. You can also investigate performance for individual components.
Follow these steps:
In the tree, select the agent for which you want performance information, for example:
SuperDomain | Host | Process |Agent | Frontends | Apps | Adaptor
Note: The Variance node and subnodes do not show Differential Analysis.