Operating system limits on heap size

The following tables group operating system heap size limitations by application server.

Heap sizing for JBoss, WebLogic, and Tomcat

Heap sizing for WebSphere

Although IBM recommends that the initial Java heap size for WebSphere not be set to the maximum Java heap size, Guidewire recommends otherwise. The IBM recommendations are not optimal for PolicyCenter. With a fixed heap, you avoid performance penalties from resizing the heap on the rising edge as the system load rises, or on the falling edge as load drops off. WebSphere provides several garbage collection policies. Guidewire recommends using the generational concurrent (gencon) garbage collection policy with equal minimum and maximum heap size.

There is some variance across JVM technology with regard to memory allocation. Guidewire supports WebSphere on the IBM JVM only. The IBM JVM manages the permanent space without the use of a permanent size setting.

Heap sizing for testing

To avoid performance degradation caused by forcing the JVM to adjust between two heap size values at runtime, set the initial and maximum values to be the same. The following table provides recommended heap settings for testing, determined with single user scenarios in mind. For production, consult Guidewire Services.