Monitor the Current Trend and Forecast Heap Usage

To monitor the current trend and forecast heap usage:

1. Click the Heap tab in the left pane.
2. From the Heap Usage by Server chart, select the app server instances or a group of app server instances for which you want to view the heap usage trend and forecast.
   In the Filters field in the Trend and Forecast chart, enter the name of the app server instance.
3. To set the Regression Model, Forecast Period, and Confidence (%), click Settings.

   You can use both linear and nonlinear regression models when you’re forecasting resource usage. The linear regression model is the default option, which is used when the relationship between the predictors and the target value can be approximated with a straight line in the graph.

   When you’re predicting resource usage, try linear regression first. If the default linear regression model can’t model the specific curve that exists in your data, then you can’t get an appropriate fit with linear regression. In such scenarios, try the other regression models to see if they produce a trend that fits the curve of your actual data better:

   • BestFit: A line shown in the graph with the same number of data points on each side of the line. The line is in the median position, but it doesn’t go from the first data point to the last data point.

   • Exponent: A base and an exponent. For example, 2³. In this example, 2 is the base and 3 is the exponent.

   • NlogN: A logarithm of a number that’s the exponent to which the value of the base is increased to produce that number. It’s also referred to as repeated multiplication.

   • Quadratic: A curve created by the intersection of a cone and a plane parallel to the side of the cone.

   From the Trend and Forecast chart, you can view the following metrics:

   • Heap size after garbage collection

   • Heap size after garbage collection according to the selected regression model

   • Maximum heap size

   Figure 3-12 Trend and Forecast Chart for Heap Usage

   
   
   Description of "Figure 3-12 Trend and Forecast Chart for Heap Usage"
   

   From this chart you can identify whether you need to expand resources to accommodate future heap usage.