Just-In-Time compiler

A Just-In-Time (JIT) compiler is a platform-specific compiler that generates machine instructions for each method as needed.

For more information about using the JIT compiler, and about the difference between the JIT compiler and direct processing, see the following pages:

Java™ runtime performance considerations.

Comparison of the JIT compiler and direct processing.

Note: The default setting for i5/OS™ is to interpret (not compile) Java methods by using the Mixed-Mode Interpreter (MMI). MMI profiles each Java method as it interprets it. After reaching the threshold specified by the os400.jit.mmi.threshold property, MMI then specifies that i5/OS use the JIT compiler to compile the method.

For more information, see the entries for the java.compiler property and the os400.jit.mmi.threshold property in the appropriate list of Java system properties:

Java system properties for Java 2 SDK (J2SDK), Standard Edition

Comparison of Just-In-Time compiler and direct processing
If you are trying to decide whether to use the Just-In-Time compiler or direct processing mode to run your Java program, this table provides additional information to help you make the best choice for your situation.

Parent topic: Java performance considerations