You will need SOA Suite installed for this recipe, and will need permission to execute the domain control scripts, as well as the HotSpot JVM tools. This recipe assumes that your SOA Suite application is running such that we may run jstat against it.

The tools jps and jstat are included with both the HotSpot and JRockit JVMs. For brevity, this recipe assumes that you have the relevant bin directory on your path. If you do not, simply use the fully qualified paths to the relevant bin directory.

This recipe assumes you are using HotSpot, as JRockit does not have a permanent generation.

jstat is a JVM tool that can be used to view a number of runtime statistics regarding the JVM. The option –gc printsthe statistics about garbage collection, including the capacity and utilization of each memory pool. In the preceding example, the parameter –h10 prints the headers every 10 lines, to make the output easier to read, and 2000 is the time in milliseconds between each sample (2 seconds).

Permanent generation is the section of JVM memory that is used to store classes and other objects that cannot be represented as Java types. The larger a SOA Suite application is, the more classes it will contain, and the more permanent generation it will need. If the permanent generation is too small, classes will need to be unloaded and reloaded in the permanent generation, causing full garbage collections to occur, and a performance hit. We want permanent generation to be large enough to hold all the classes in your SOA Suite application, with a little overhead for other resources, so if the utilization of the permanent generation is around 80 percent of its capacity, we should have sufficient overhead to prevent classes needing to be unloaded.