62 lines
4.1 KiB
HTML
62 lines
4.1 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Release-to-release compatibility" />
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<meta name="abstract" content="Java class files are upward compatible (JDK 1.1.x to 1.2.x to 1.3.x to 1.4.x to 1.5.x) as long as they do not make use of a feature for which Sun has dropped or changed support." />
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<meta name="description" content="Java class files are upward compatible (JDK 1.1.x to 1.2.x to 1.3.x to 1.4.x to 1.5.x) as long as they do not make use of a feature for which Sun has dropped or changed support." />
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<meta name="DC.Relation" scheme="URI" content="whatitis.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rtrcomp" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Release-to-release compatibility</title>
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</head>
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<body id="rtrcomp"><a name="rtrcomp"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Release-to-release compatibility</h1>
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<div><p>Java™ class files are upward compatible (JDK 1.1.x to
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1.2.x to 1.3.x to 1.4.x to 1.5.x) as long as they do not make use of a feature
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for which Sun has dropped or changed support.</p>
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<p>See <a href="http://www.java.sun.com/" target="_blank">The
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Source for Java Technology java.sun.com</a> for information
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on release-to-release availability.</p>
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<p>When Java programs on an iSeries™ server are optimized using <a href="../cl/crtjvapgm.htm" target="_blank">Create Java Program
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(CRTJVAPGM) command</a>, a Java Program (JVAPGM) is attached to the
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class file. The internal structure of these JVAPGMs changed on V4R4. This
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means that JVAPGMs created before V4R4 are not valid on V4R4 and later releases.
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You must recreate the JVAPGMs or the system automatically creates a JVAPGM
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at the same optimization level as before. It is, however, recommended that
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you manually perform a CRTJVAPGM, especially with JAR or ZIP files. This produces
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the best optimization with the smallest program size.</p>
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<p>For best performance at optimization level 40, it is recommended to preform
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CRTJVAPGM on each <span class="keyword">i5/OS™</span> release
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or JDK version change. This is especially true if the JDKVER facility is used
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on CRTJVAPGM, as this results in methods from the Sun JDK being inlined into
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your JVAPGM. This can be a great advantage to performance. If, however, changes
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are made in the JDK on subsequent releases that invalidate those inlines,
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the programs may actually run slower than at lower optimizations. This is
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because special case code must be run to get proper operation.</p>
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<p>See <a href="runtperf.htm">Java runtime performance</a> for more
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detailed performance information.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="whatitis.htm" title="Java compatibleIBM Developer Kit for Java is optimized for use in an iSeries server environment. It uses the compatibility of Java programming and user interfaces, so you can develop your own applications for the iSeries server.">IBM Developer Kit for Java</a></div>
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</div>
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</div>
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</body>
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</html>
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