Full-Speed Debug

The iSeries™ Java™ Virtual Machine (JVM) now supports "full-speed debugging". Prior to V5R3, enabling debugging meant disabling the Just-In-Time (JIT) compiler. Application performance suffered because many methods had to be run with the slow interpreter. This significant performance degradation was especially difficult for applications that could run for days before getting to the point where you wished to begin debugging.

Full-speed debug allows you to run your application with all the performance benefits of JIT compiled code without losing the ability to perform some of the most common debugging activities, such as setting breakpoints, stepping through code, and viewing local variables.

Since full-speed debug allows methods to be JIT compiled, there are a couple of limitations on debugging:

• Step operations on return statements do not work if the caller is compiled code.
• Watchpoints only trigger in non-compiled methods that modify the watched field.