The client VM is tuned for reducing start-up time and memory footprint. Invoke it by using the -client JVM command-line option.
The server VM is designed for maximum program execution speed. Invoke it by using the -server JVM command-line option.
By default, the Application Server uses the JVM setting appropriate to the purpose:
Platform Edition, targeted at application developers, uses the -client JVM flag to optimize startup performance and conserve memory resources.
Enterprise Edition, targeted at production deployments, uses the default JVM startup mode. With J2SE 5.0, the HotSpot VM provides server-class machine detection, which will use the server VM if it detects “server-class” hardware (at least two CPUs and two GB of physical memory).
You can override the default by changing the JVM settings in the Admin Console under Configurations > config-name > JVM Settings (JVM Options).
For more information on server-class machine detection in J2SE 5.0, see Server-Class Machine Detection .
For more information on JVMs, see JavaTM Virtual Machines.