How to identify/determine the maximum JVM Heap Size for OC4j components in R12 / 10gAS

Below command will help you to identify the maximum memory heap size than can be allocated to a JVM process.

java -mx[value]m -version

Start with a higher value like 4G or higher and slowly cut down to the maximum allowed value.

Sample

$ java -mx4096m -version

Invalid maximum heap size: -Xmx4096m

The specified size exceeds the maximum representable size.

Could not create the Java virtual machine.

As you can see my system can't support 4GB for a JVM.

Now lets reduce to a lesser value like 3GB

$ java -mx3072m -version

Invalid maximum heap size: -Xmx3072m

The specified size exceeds the maximum representable size.

Could not create the Java virtual machine.

As you can see my system can't support 3GB for a JVM.

Now again lets reduce to a lesser value like 2.5GB

$ java -mx2560m -version

java version "1.6.0_10"

Java(TM) SE Runtime Environment (build 1.6.0_10-b33)

Java HotSpot(TM) Server VM (build 11.0-b15, mixed mode)

Now its clear that the maximum allowed value is 2.5 GB.