The Java Virtual Machine (JVM) heap is an independent memory allocation that can reduce the capacity of the main memory heap.
Every execution group creates its own Java Virtual Machine (JVM). The execution group uses the JVM to execute the internal administration threads that require Java. This usage is typically minimal. The primary use of the JVM is for IBM primitive nodes that make use of Java functionality. These primitives include:
From WebSphere Business Integration Message Broker Version 5.0 onwards, the JVM is created with a minimum of 128 MB of space allocated and reserved for its use. As with any JVM, you can pass parameters in to set the minimum and maximum heap sizes.
To give more capacity to a message flow that is going to process large messages, reduce the minimum JVM heap size to allow the main memory heap to occupy more address space. For details of how to reduce the minimum JVM heap size, see Setting the JVM heap size.