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<meta name="abstract" content="The iSeries Java Virtual Machine (JVM) now supports &#34;full-speed debugging&#34;. 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." />
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<h1 class="topictitle1">Full-Speed Debug</h1>
<div><p>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.</p>
<p>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.</p>
<p>Since full-speed debug allows methods to be JIT compiled, there are a couple
of limitations on debugging: </p>
<ul><li>Step operations on return statements do not work if the caller is compiled
code. </li>
<li>Watchpoints only trigger in non-compiled methods that modify the watched
field. </li>
</ul>
<div class="note"><span class="notetitle">Note:</span> This feature is only supported for debuggers that use the Java Debug
Wire Protocol (JDWP) to perform debugging operations. The system debugger
currently does not support full-speed debug. </div>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="jpdebuga.htm" title="The Java Platform Debugger Architecture (JPDA) consists of the JVM Debug Interface/JVM Tool Interface, the Java Debug Wire Protocol, and the Java Debug Interface. All these parts of the JPDA enable any front end of a debugger that uses the JDWP to perform debugging operations. The debugger front end can either run remotely or run as an iSeries application.">Java Platform Debugger Architecture</a></div>
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