Setting the JVM heap size

When you start an execution group, it creates a Java™ virtual machine (JVM) for executing a Java user-defined node.

You can pass parameters to the JVM 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.

You do not need to increase the maximum heap size unless you use Java intensively with, for example, user-defined nodes.

Use caution when you set the maximum heap size because the Java Runtime Environment takes the values for its initial, maximum, and current heap sizes to calculate how frequently it drives garbage collection. A large maximum heap size drives garbage collection less frequently. If garbage collection is driven less frequently, the DataFlowEngine heap size continues to grow.

Start of changeUse the information on JVM parameter values within the mqsichangeproperties command to set the heap size you require.End of change

Related concepts
JVM heap sizing
Stack storage
Related tasks
Optimizing message flow response times
Related reference
Message flows
JVM parameter values
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Copyright IBM Corporation 1999, 2009Copyright IBM Corporation 1999, 2009.
Last updated : 2009-01-07 15:20:45

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