<!--
* Copyright (c) 2017, 2018 IBM Corp. and others
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/legal/epl-2.0/ or the Apache
* License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the
* following Secondary Licenses when the conditions for such
* availability set forth in the Eclipse Public License, v. 2.0
* are satisfied: GNU General Public License, version 2 with
* the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH
* Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
-->


<!DOCTYPE html>
<html lang="en" class="no-js">
  <head>
    
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width,initial-scale=1">
      <meta http-equiv="x-ua-compatible" content="ie=edge">
      
        <meta name="description" content="Eclipse OpenJ9 documentation">
      
      
        <link rel="canonical" href="https://www.eclipse.org/openj9/docs/">
      
      
        <meta name="lang:clipboard.copy" content="">
      
        <meta name="lang:clipboard.copied" content="">
      
        <meta name="lang:search.language" content="">
      
        <meta name="lang:search.pipeline.stopwords" content="">
      
        <meta name="lang:search.pipeline.trimmer" content="">
      
        <meta name="lang:search.result.none" content="">
      
        <meta name="lang:search.result.one" content="">
      
        <meta name="lang:search.result.other" content="">
      
        <meta name="lang:search.tokenizer" content="">
      
      <link rel="shortcut icon" href="./cr/oj9logo_img9.ico">
      <meta name="generator" content="mkdocs-0.17.2, mkdocs-material-2.6.3">
    
    
        <title> </title>
      
    
      <link rel="stylesheet" href="./assets/stylesheets/application.9b572555.css">
      
        <link rel="stylesheet" href="./assets/stylesheets/application-palette.6079476c.css">
      
    
      <script src="./assets/javascripts/modernizr.1aa3b519.js"></script>
    
    
        <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto:300,400,400i,700|Roboto+Mono">
        <style>body,input{font-family:"Roboto","Helvetica Neue",Helvetica,Arial,sans-serif}code,kbd,pre{font-family:"Roboto Mono","Courier New",Courier,monospace}</style>
      
      <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
    
    
      <link rel="stylesheet" href="./stylesheets/oj9.css">
    
    
  </head>
  
    
    <body dir="" data-md-color-primary="cyan" data-md-color-accent="cyan">
  
    <svg class="md-svg">
      <defs>
        
        
          <svg xmlns="http://www.w3.org/2000/svg" width="416" height="448"
    viewBox="0 0 416 448" id="github">
  <path fill="currentColor" d="M160 304q0 10-3.125 20.5t-10.75 19-18.125
        8.5-18.125-8.5-10.75-19-3.125-20.5 3.125-20.5 10.75-19 18.125-8.5
        18.125 8.5 10.75 19 3.125 20.5zM320 304q0 10-3.125 20.5t-10.75
        19-18.125 8.5-18.125-8.5-10.75-19-3.125-20.5 3.125-20.5 10.75-19
        18.125-8.5 18.125 8.5 10.75 19 3.125 20.5zM360
        304q0-30-17.25-51t-46.75-21q-10.25 0-48.75 5.25-17.75 2.75-39.25
        2.75t-39.25-2.75q-38-5.25-48.75-5.25-29.5 0-46.75 21t-17.25 51q0 22 8
        38.375t20.25 25.75 30.5 15 35 7.375 37.25 1.75h42q20.5 0
        37.25-1.75t35-7.375 30.5-15 20.25-25.75 8-38.375zM416 260q0 51.75-15.25
        82.75-9.5 19.25-26.375 33.25t-35.25 21.5-42.5 11.875-42.875 5.5-41.75
        1.125q-19.5 0-35.5-0.75t-36.875-3.125-38.125-7.5-34.25-12.875-30.25-20.25-21.5-28.75q-15.5-30.75-15.5-82.75
        0-59.25 34-99-6.75-20.5-6.75-42.5 0-29 12.75-54.5 27 0 47.5 9.875t47.25
        30.875q36.75-8.75 77.25-8.75 37 0 70 8 26.25-20.5
        46.75-30.25t47.25-9.75q12.75 25.5 12.75 54.5 0 21.75-6.75 42 34 40 34
        99.5z" />
</svg>
        
      </defs>
    </svg>
    <input class="md-toggle" data-md-toggle="drawer" type="checkbox" id="drawer">
    <input class="md-toggle" data-md-toggle="search" type="checkbox" id="search">
    <label class="md-overlay" data-md-component="overlay" for="drawer"></label>
    
      <a href="#eclipse-openj9" tabindex="1" class="md-skip">
        
      </a>
    
    
      <!--
* Copyright (c) 2017, 2018 IBM Corp. and others
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/legal/epl-2.0/ or the Apache
* License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the
* following Secondary Licenses when the conditions for such
* availability set forth in the Eclipse Public License, v. 2.0
* are satisfied: GNU General Public License, version 2 with
* the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH
* Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
-->
<header class="md-header" data-md-component="header">
  <nav class="md-header-nav md-grid">
    <div class="md-flex">
      <div class="md-flex__cell md-flex__cell--shrink">
        <a href="https://www.eclipse.org/openj9/docs" title=" " class="md-header-nav__button md-logo">
          
            <img src="./cr/openj9_6b.png">
          
        </a>
      </div>
      <div class="md-flex__cell md-flex__cell--shrink">
        <label class="md-icon md-icon--menu md-header-nav__button" for="drawer"></label>
      </div>
      <div class="md-flex__cell md-flex__cell--stretch">
        <div class="md-flex__ellipsis md-header-nav__title" data-md-component="title">
        </div>
      </div>
      <div class="md-flex__cell md-flex__cell--shrink">
        
          
            <label class="md-icon md-icon--search md-header-nav__button" for="search"></label>
            
<div class="md-search" data-md-component="search" role="dialog">
  <label class="md-search__overlay" for="search"></label>
  <div class="md-search__inner" role="search">
    <form class="md-search__form" name="search">
      <input type="text" class="md-search__input" name="query" placeholder="Search" autocapitalize="off" autocorrect="off" autocomplete="off" spellcheck="false" data-md-component="query" data-md-state="active">
      <label class="md-icon md-search__icon" for="search"></label>
      <button type="reset" class="md-icon md-search__icon" data-md-component="reset" tabindex="-1">
        &#xE5CD;
      </button>
    </form>
    <div class="md-search__output">
      <div class="md-search__scrollwrap" data-md-scrollfix>
        <div class="md-search-result" data-md-component="result">
          <div class="md-search-result__meta">
            
          </div>
          <ol class="md-search-result__list"></ol>
        </div>
      </div>
    </div>
  </div>
</div>
          
        
      </div>
      
        <div class="md-flex__cell md-flex__cell--shrink">
          <div class="md-header-nav__source">
            

  <a href="https://github.com/eclipse/openj9-docs/" title="Go to repository" class="md-source" data-md-source="github">
    
      <div class="md-source__icon">
        <svg viewBox="0 0 24 24" width="24" height="24">
          <use xlink:href="#github" width="24" height="24"></use>
        </svg>
      </div>
    
    <div class="md-source__repository">
      GitHub
    </div>
  </a>

          </div>
        </div>
      

      <!-- Eclipse Incubator link -->
      <div class="md-flex__cell md-flex__cell--shrink">
        <a href="http://wiki.eclipse.org/Development_Resources/Process_Guidelines/What_is_Incubation" target="_blank"><img class="egg" src="./cr/egg-incubation.png" alt="Eclipse Incubation"></a>
      </div>  

    </div>
  </nav>
</header>
    
    <div class="md-container">
      
        
      <main class="md-main">
        <div class="md-main__inner md-grid" data-md-component="container">
          
            
              <div class="md-sidebar md-sidebar--primary" data-md-component="navigation">
                <div class="md-sidebar__scrollwrap">
                  <div class="md-sidebar__inner">
                    <nav class="md-nav md-nav--primary" data-md-level="0">
  <label class="md-nav__title md-nav__title--site" for="drawer">
    <span class="md-nav__button md-logo">
      
        <img src="./cr/openj9_6b.png" width="24" height="24">
      
    </span>
     
  </label>
  
    <div class="md-nav__source">
      

  <a href="https://github.com/eclipse/openj9-docs/" title="Go to repository" class="md-source" data-md-source="github">
    
      <div class="md-source__icon">
        <svg viewBox="0 0 24 24" width="24" height="24">
          <use xlink:href="#github" width="24" height="24"></use>
        </svg>
      </div>
    
    <div class="md-source__repository">
      GitHub
    </div>
  </a>

    </div>
  
  <ul class="md-nav__list" data-md-scrollfix>
    
      
  <li class="md-nav__item md-nav__item--active">
    
    <input class="md-toggle md-nav__toggle" data-md-toggle="toc" type="checkbox" id="toc">
    
      
      <label class="md-nav__link md-nav__link--active" for="toc">
        Introduction
      </label>
    
    <a href="." title="Introduction" class="md-nav__link md-nav__link--active">
      Introduction
    </a>
    
      
<nav class="md-nav md-nav--secondary">
  
  
    <label class="md-nav__title" for="toc">On this page ...</label>
    <ul class="md-nav__list" data-md-scrollfix>
      
        <li class="md-nav__item">
  <a href="#what-is-openj9" title="What is OpenJ9" class="md-nav__link">
    What is OpenJ9
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#useful-links" title="Useful links" class="md-nav__link">
    Useful links
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#configuring-your-system" title="Configuring your system" class="md-nav__link">
    Configuring your system
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#performance-tuning" title="Performance tuning" class="md-nav__link">
    Performance tuning
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#runtime-options" title="Runtime options" class="md-nav__link">
    Runtime options
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#default-settings" title="Default settings" class="md-nav__link">
    Default settings
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#supported-environments" title="Supported environments" class="md-nav__link">
    Supported environments
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#troubleshooting" title="Troubleshooting" class="md-nav__link">
    Troubleshooting
  </a>
  
</li>
      
      
    </ul>
  
</nav>
    
  </li>

    
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-2" type="checkbox" id="nav-2">
    
    <label class="md-nav__link" for="nav-2">
      Release notes
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
      <label class="md-nav__title" for="nav-2">
        Release notes
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="version0.9/" title="Version 0.9.0" class="md-nav__link">
      Version 0.9.0
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="version0.8/" title="Version 0.8.0" class="md-nav__link">
      Version 0.8.0
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

    
  <li class="md-nav__item">
    <a href="gc/" title="Garbage Collection" class="md-nav__link">
      Garbage Collection
    </a>
  </li>

    
  <li class="md-nav__item">
    <a href="jit/" title="JIT Compiler" class="md-nav__link">
      JIT Compiler
    </a>
  </li>

    
  <li class="md-nav__item">
    <a href="aot/" title="AOT Compiler" class="md-nav__link">
      AOT Compiler
    </a>
  </li>

    
  <li class="md-nav__item">
    <a href="shrc/" title="Class data sharing" class="md-nav__link">
      Class data sharing
    </a>
  </li>

    
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-7" type="checkbox" id="nav-7">
    
    <label class="md-nav__link" for="nav-7">
      Diagnostics
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
      <label class="md-nav__title" for="nav-7">
        Diagnostics
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="diag_overview/" title="Tools and data" class="md-nav__link">
      Tools and data
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dump_javadump/" title="Java dump" class="md-nav__link">
      Java dump
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dump_heapdump/" title="Heap dump" class="md-nav__link">
      Heap dump
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dump_systemdump/" title="System dump" class="md-nav__link">
      System dump
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

    
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-8" type="checkbox" id="nav-8">
    
    <label class="md-nav__link" for="nav-8">
      Command-line options
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
      <label class="md-nav__title" for="nav-8">
        Command-line options
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="cmdline_specifying/" title="Specifying options" class="md-nav__link">
      Specifying options
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="cmdline_general/" title="Standard options" class="md-nav__link">
      Standard options
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="cmdline_migration/" title="Migrating to OpenJ9" class="md-nav__link">
      Migrating to OpenJ9
    </a>
  </li>

        
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-8-4" type="checkbox" id="nav-8-4">
    
    <label class="md-nav__link" for="nav-8-4">
      System property options
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="2">
      <label class="md-nav__title" for="nav-8-4">
        System property options
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="d_jvm_commands/" title="Using System properties" class="md-nav__link">
      Using System properties
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmenableclasscaching/" title="-Dcom.ibm.enableClassCaching" class="md-nav__link">
      -Dcom.ibm.enableClassCaching
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmenablelegacydumpsecurity/" title="-Dcom.ibm.enableLegacyDumpSecurity" class="md-nav__link">
      -Dcom.ibm.enableLegacyDumpSecurity
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmenablelegacylogsecurity/" title="-Dcom.ibm.enableLegacyLogSecurity" class="md-nav__link">
      -Dcom.ibm.enableLegacyLogSecurity
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmenablelegacytracesecurity/" title="-Dcom.ibm.enableLegacyTraceSecurity" class="md-nav__link">
      -Dcom.ibm.enableLegacyTraceSecurity
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmlangmanagementosmxbeaniscputime100ns/" title="-Dcom.ibm.lang.management.OperatingSystemMXBean.isCpuTime100ns" class="md-nav__link">
      -Dcom.ibm.lang.management.OperatingSystemMXBean.isCpuTime100ns
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmlangmanagementverbose/" title="-Dcom.ibm.lang.management.verbose" class="md-nav__link">
      -Dcom.ibm.lang.management.verbose
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmtoolsattachdirectory/" title="-Dcom.ibm.tools.attach.directory" class="md-nav__link">
      -Dcom.ibm.tools.attach.directory
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmtoolsattachdisplayname/" title="-Dcom.ibm.tools.attach.displayName" class="md-nav__link">
      -Dcom.ibm.tools.attach.displayName
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmtoolsattachenable/" title="-Dcom.ibm.tools.attach.enable" class="md-nav__link">
      -Dcom.ibm.tools.attach.enable
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmtoolsattachid/" title="-Dcom.ibm.tools.attach.id" class="md-nav__link">
      -Dcom.ibm.tools.attach.id
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dcomibmtoolsattachtimeout/" title="-Dcom.ibm.tools.attach.timeout" class="md-nav__link">
      -Dcom.ibm.tools.attach.timeout
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="dfileencoding/" title="-Dfile.encoding" class="md-nav__link">
      -Dfile.encoding
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="djavacompiler/" title="-Djava.compiler" class="md-nav__link">
      -Djava.compiler
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

        
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-8-5" type="checkbox" id="nav-8-5">
    
    <label class="md-nav__link" for="nav-8-5">
      JVM -X options
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="2">
      <label class="md-nav__title" for="nav-8-5">
        JVM -X options
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="x_jvm_commands/" title="Using -X options" class="md-nav__link">
      Using -X options
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="x/" title="-X" class="md-nav__link">
      -X
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xaggressive/" title="-Xaggressive" class="md-nav__link">
      -Xaggressive
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xalwaysclassgc/" title="-Xalwaysclassgc" class="md-nav__link">
      -Xalwaysclassgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xaot/" title="-Xaot" class="md-nav__link">
      -Xaot
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xargencoding/" title="-Xargencoding" class="md-nav__link">
      -Xargencoding
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xbootclasspath/" title="-Xbootclasspath" class="md-nav__link">
      -Xbootclasspath
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xceehdlr/" title="-XCEEHDLR" class="md-nav__link">
      -XCEEHDLR
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcheck/" title="-Xcheck" class="md-nav__link">
      -Xcheck
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xclassgc/" title="-Xclassgc" class="md-nav__link">
      -Xclassgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcodecache/" title="-Xcodecache" class="md-nav__link">
      -Xcodecache
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcodecachetotal/" title="-Xcodecachetotal" class="md-nav__link">
      -Xcodecachetotal
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcomp/" title="-Xcomp" class="md-nav__link">
      -Xcomp
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompactexplicitgc/" title="-Xcompactexplicitgc" class="md-nav__link">
      -Xcompactexplicitgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompactgc/" title="-Xcompactgc" class="md-nav__link">
      -Xcompactgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompilationthreads/" title="-XcompilationThreads" class="md-nav__link">
      -XcompilationThreads
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompressedrefs/" title="-Xcompressedrefs" class="md-nav__link">
      -Xcompressedrefs
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xconcurrentbackground/" title="-Xconcurrentbackground" class="md-nav__link">
      -Xconcurrentbackground
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xconcurrentlevel/" title="-Xconcurrentlevel" class="md-nav__link">
      -Xconcurrentlevel
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xconcurrentslack/" title="-Xconcurrentslack" class="md-nav__link">
      -Xconcurrentslack
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xconmeter/" title="-Xconmeter" class="md-nav__link">
      -Xconmeter
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xdiagnosticscollector/" title="-Xdiagnosticscollector" class="md-nav__link">
      -Xdiagnosticscollector
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xenableexcessivegc/" title="-Xdisableexcessivegc" class="md-nav__link">
      -Xdisableexcessivegc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xenableexplicitgc/" title="-Xdisableexplicitgc" class="md-nav__link">
      -Xdisableexplicitgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xdisablejavadump/" title="-Xdisablejavadump" class="md-nav__link">
      -Xdisablejavadump
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xenablestringconstantgc/" title="-Xdisablestringconstantgc" class="md-nav__link">
      -Xdisablestringconstantgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xdump/" title="-Xdump" class="md-nav__link">
      -Xdump
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xenableexcessivegc/" title="-Xenableexcessivegc" class="md-nav__link">
      -Xenableexcessivegc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xenableexplicitgc/" title="-Xenableexplicitgc" class="md-nav__link">
      -Xenableexplicitgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xenablestringconstantgc/" title="-Xenablestringconstantgc" class="md-nav__link">
      -Xenablestringconstantgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xfastresolve/" title="-Xfastresolve" class="md-nav__link">
      -Xfastresolve
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xfuture/" title="-Xfuture" class="md-nav__link">
      -Xfuture
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xgc/" title="-Xgc" class="md-nav__link">
      -Xgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xgcsplitheap/" title="-Xgc:splitheap" class="md-nav__link">
      -Xgc:splitheap
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xgcpolicy/" title="-Xgcpolicy" class="md-nav__link">
      -Xgcpolicy
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xgcthreads/" title="-Xgcthreads" class="md-nav__link">
      -Xgcthreads
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xgcworkpackets/" title="-Xgcworkpackets" class="md-nav__link">
      -Xgcworkpackets
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xifa/" title="-Xifa" class="md-nav__link">
      -Xifa
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xint/" title="-Xint" class="md-nav__link">
      -Xint
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xss/" title="-Xiss" class="md-nav__link">
      -Xiss
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xjit/" title="-Xjit" class="md-nav__link">
      -Xjit
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xjni/" title="-Xjni" class="md-nav__link">
      -Xjni
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlinenumbers/" title="-Xlinenumbers" class="md-nav__link">
      -Xlinenumbers
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xloa/" title="-Xloa" class="md-nav__link">
      -Xloa
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xloaminimum/" title="-Xloainitial" class="md-nav__link">
      -Xloainitial
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xloaminimum/" title="-Xloamaximum" class="md-nav__link">
      -Xloamaximum
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xloaminimum/" title="-Xloaminimum" class="md-nav__link">
      -Xloaminimum
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlockreservation/" title="-XlockReservation" class="md-nav__link">
      -XlockReservation
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlockword/" title="-Xlockword" class="md-nav__link">
      -Xlockword
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlog/" title="-Xlog" class="md-nav__link">
      -Xlog
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlp/" title="-Xlp" class="md-nav__link">
      -Xlp
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlpcodecache/" title="-Xlp:codecache" class="md-nav__link">
      -Xlp:codecache
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlpobjectheap/" title="-Xlp:objectheap" class="md-nav__link">
      -Xlp:objectheap
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmine/" title="-Xmaxe" class="md-nav__link">
      -Xmaxe
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xminf/" title="-Xmaxf" class="md-nav__link">
      -Xmaxf
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmint/" title="-Xmaxt" class="md-nav__link">
      -Xmaxt
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmca/" title="-Xmca" class="md-nav__link">
      -Xmca
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmca/" title="-Xmco" class="md-nav__link">
      -Xmco
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmcrs/" title="-Xmcrs" class="md-nav__link">
      -Xmcrs
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmine/" title="-Xmine" class="md-nav__link">
      -Xmine
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xminf/" title="-Xminf" class="md-nav__link">
      -Xminf
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmint/" title="-Xmint" class="md-nav__link">
      -Xmint
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmn/" title="-Xmn" class="md-nav__link">
      -Xmn
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmn/" title="-Xmns" class="md-nav__link">
      -Xmns
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmn/" title="-Xmnx" class="md-nav__link">
      -Xmnx
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmo/" title="-Xmo" class="md-nav__link">
      -Xmo
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmo/" title="-Xmoi" class="md-nav__link">
      -Xmoi
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmo/" title="-Xmos" class="md-nav__link">
      -Xmos
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmo/" title="-Xmox" class="md-nav__link">
      -Xmox
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmr/" title="-Xmr" class="md-nav__link">
      -Xmr
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmr/" title="-Xmrx" class="md-nav__link">
      -Xmrx
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xms/" title="-Xms" class="md-nav__link">
      -Xms
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xmso/" title="-Xmso" class="md-nav__link">
      -Xmso
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xms/" title="-Xmx" class="md-nav__link">
      -Xmx
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xaot/" title="-Xnoaot" class="md-nav__link">
      -Xnoaot
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xclassgc/" title="-Xnoclassgc" class="md-nav__link">
      -Xnoclassgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompactexplicitgc/" title="-Xnocompactexplicitgc" class="md-nav__link">
      -Xnocompactexplicitgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompactgc/" title="-Xnocompactgc" class="md-nav__link">
      -Xnocompactgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xcompressedrefs/" title="-Xnocompressedrefs" class="md-nav__link">
      -Xnocompressedrefs
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xjit/" title="-Xnojit" class="md-nav__link">
      -Xnojit
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xlinenumbers/" title="-Xnolinenumbers" class="md-nav__link">
      -Xnolinenumbers
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xloa/" title="-Xnoloa" class="md-nav__link">
      -Xnoloa
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsigcatch/" title="-Xnosigcatch" class="md-nav__link">
      -Xnosigcatch
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsigchain/" title="-Xnosigchain" class="md-nav__link">
      -Xnosigchain
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xnumanone/" title="-Xnuma:none" class="md-nav__link">
      -Xnuma:none
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xoptionsfile/" title="-Xoptionsfile" class="md-nav__link">
      -Xoptionsfile
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xquickstart/" title="-Xquickstart" class="md-nav__link">
      -Xquickstart
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xrdbginfo/" title="-Xrdbginfo" class="md-nav__link">
      -Xrdbginfo
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xrs/" title="-Xrs" class="md-nav__link">
      -Xrs
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsamplingexpirationtime/" title="-XsamplingExpirationTime" class="md-nav__link">
      -XsamplingExpirationTime
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xscdmx/" title="-Xscdmx" class="md-nav__link">
      -Xscdmx
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xscminaot/" title="-Xscmaxaot" class="md-nav__link">
      -Xscmaxaot
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xscminjitdata/" title="-Xscmaxjitdata" class="md-nav__link">
      -Xscmaxjitdata
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xscminaot/" title="-Xscminaot" class="md-nav__link">
      -Xscminaot
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xscminjitdata/" title="-Xscminjitdata" class="md-nav__link">
      -Xscminjitdata
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xscmx/" title="-Xscmx" class="md-nav__link">
      -Xscmx
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xshareclasses/" title="-Xshareclasses" class="md-nav__link">
      -Xshareclasses
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsigcatch/" title="-Xsigcatch" class="md-nav__link">
      -Xsigcatch
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsigchain/" title="-Xsigchain" class="md-nav__link">
      -Xsigchain
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsignal/" title="-Xsignal" class="md-nav__link">
      -Xsignal
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsoftmx/" title="-Xsoftmx" class="md-nav__link">
      -Xsoftmx
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xsoftrefthreshold/" title="-Xsoftrefthreshold" class="md-nav__link">
      -Xsoftrefthreshold
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xss/" title="-Xss" class="md-nav__link">
      -Xss
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xss/" title="-Xssi" class="md-nav__link">
      -Xssi
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xtgc/" title="-Xtgc" class="md-nav__link">
      -Xtgc
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xthr/" title="-Xthr" class="md-nav__link">
      -Xthr
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xtlhprefetch/" title="-XtlhPrefetch" class="md-nav__link">
      -XtlhPrefetch
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xtrace/" title="-Xtrace" class="md-nav__link">
      -Xtrace
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xtunevirtualized/" title="-Xtune:virtualized" class="md-nav__link">
      -Xtune:virtualized
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xverbosegclog/" title="-Xverbosegclog" class="md-nav__link">
      -Xverbosegclog
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xverify/" title="-Xverify" class="md-nav__link">
      -Xverify
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xzero/" title="-Xzero" class="md-nav__link">
      -Xzero
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

        
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-8-6" type="checkbox" id="nav-8-6">
    
    <label class="md-nav__link" for="nav-8-6">
      JVM -XX: options
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="2">
      <label class="md-nav__title" for="nav-8-6">
        JVM -XX: options
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="xx_jvm_commands/" title="Using -XX options" class="md-nav__link">
      Using -XX options
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxactiveprocessorcount/" title="-XXActiveProcessorCount" class="md-nav__link">
      -XXActiveProcessorCount
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxallowvmshutdown/" title="-XXallowvmshutdown" class="md-nav__link">
      -XXallowvmshutdown
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxcodecachetotal/" title="-XX:codecachetotal" class="md-nav__link">
      -XX:codecachetotal
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxdisableexplicitgc/" title="-XX:[+|-]DisableExplicitGC" class="md-nav__link">
      -XX:[+|-]DisableExplicitGC
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxdisclaimjitscratch/" title="-XX:[+|-]DisclaimJitScratch" class="md-nav__link">
      -XX:[+|-]DisclaimJitScratch
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxenablecpumonitor/" title="-XX:[+|-]EnableCPUMonitor" class="md-nav__link">
      -XX:[+|-]EnableCPUMonitor
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxhandlesigxfsz/" title="-XX:[+|-]handleSIGXFSZ" class="md-nav__link">
      -XX:[+|-]handleSIGXFSZ
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxheapdumponoutofmemory/" title="-XX:[+|-]HeapDumpOnOutOfMemory" class="md-nav__link">
      -XX:[+|-]HeapDumpOnOutOfMemory
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxheapdumppath/" title="-XX:HeapDumpPath" class="md-nav__link">
      -XX:HeapDumpPath
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxheapmanagementmxbeancompatibility/" title="-XX:[+|-]HeapManagementMXBeanCompatibility" class="md-nav__link">
      -XX:[+|-]HeapManagementMXBeanCompatibility
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxidletuningcompactonidle/" title="-XX:[+|-]IdleTuningCompactOnIdle" class="md-nav__link">
      -XX:[+|-]IdleTuningCompactOnIdle
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxidletuninggconidle/" title="-XX:[+|-]IdleTuningGcOnIdle" class="md-nav__link">
      -XX:[+|-]IdleTuningGcOnIdle
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxidletuningminfreeheaponidle/" title="-XX:IdleTuningMinFreeHeapOnIdle" class="md-nav__link">
      -XX:IdleTuningMinFreeHeapOnIdle
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxidletuningminidlewaittime/" title="-XX:IdleTuningMinIdleWaitTime" class="md-nav__link">
      -XX:IdleTuningMinIdleWaitTime
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxignoreunrecognizedvmoptions/" title="-XX:[+|-]IgnoreUnrecognizedVMOptions" class="md-nav__link">
      -XX:[+|-]IgnoreUnrecognizedVMOptions
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxinitialrampercentage/" title="-XX:InitialRAMPercentage" class="md-nav__link">
      -XX:InitialRAMPercentage
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxinterleavememory/" title="-XX:[+|-]InterleaveMemory" class="md-nav__link">
      -XX:[+|-]InterleaveMemory
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxlazysymbolresolution/" title="-XX:[+|-]LazySymbolResolution" class="md-nav__link">
      -XX:[+|-]LazySymbolResolution
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxmaxdirectmemorysize/" title="-XX:MaxDirectMemorySize" class="md-nav__link">
      -XX:MaxDirectMemorySize
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxmaxrampercentage/" title="-XX:MaxRAMPercentage" class="md-nav__link">
      -XX:MaxRAMPercentage
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxnosuballoc32bitmem/" title="-XXnosuballoc32bitmem" class="md-nav__link">
      -XXnosuballoc32bitmem
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxpagealigndirectmemory/" title="-XX:[+|-]PageAlignDirectMemory" class="md-nav__link">
      -XX:[+|-]PageAlignDirectMemory
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxreducecpumonitoroverhead/" title="-XX:[+|-]ReduceCPUMonitorOverhead" class="md-nav__link">
      -XX:[+|-]ReduceCPUMonitorOverhead
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxruntimeinstrumentation/" title="-XX:[+|-]RuntimeInstrumentation" class="md-nav__link">
      -XX:[+|-]RuntimeInstrumentation
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxsethwprefetch/" title="-XXsetHWPrefetch" class="md-nav__link">
      -XXsetHWPrefetch
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxshareclassesenablebci/" title="-XX:ShareClassesDisableBCI" class="md-nav__link">
      -XX:ShareClassesDisableBCI
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxshareclassesenablebci/" title="-XX:ShareClassesEnableBCI" class="md-nav__link">
      -XX:ShareClassesEnableBCI
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxsharedcachehardlimit/" title="-XX:SharedCacheHardLimit" class="md-nav__link">
      -XX:SharedCacheHardLimit
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxstacktraceinthrowable/" title="-XX:-StackTraceInThrowable" class="md-nav__link">
      -XX:-StackTraceInThrowable
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxusecompressedoops/" title="-XX:[+|-]UseCompressedOops" class="md-nav__link">
      -XX:[+|-]UseCompressedOops
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxusecontainersupport/" title="-XX:[+|-]UseContainerSupport" class="md-nav__link">
      -XX:[+|-]UseContainerSupport
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxusenogc/" title="-XX:[+|-]UseNoGC" class="md-nav__link">
      -XX:[+|-]UseNoGC
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxverboseverification/" title="-XX:[+|-]VerboseVerification" class="md-nav__link">
      -XX:[+|-]VerboseVerification
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="xxvmlockclassloader/" title="-XX:[+|-]VMLockClassLoader" class="md-nav__link">
      -XX:[+|-]VMLockClassLoader
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

        
      </ul>
    </nav>
  </li>

    
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-9" type="checkbox" id="nav-9">
    
    <label class="md-nav__link" for="nav-9">
      Tools
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
      <label class="md-nav__title" for="nav-9">
        Tools
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="tool_jdmpview/" title="Dump viewer" class="md-nav__link">
      Dump viewer
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="tool_traceformat/" title="Trace formatter" class="md-nav__link">
      Trace formatter
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

    
  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-10" type="checkbox" id="nav-10">
    
    <label class="md-nav__link" for="nav-10">
       Reference
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
      <label class="md-nav__title" for="nav-10">
         Reference
      </label>
      <ul class="md-nav__list" data-md-scrollfix>
        
        
  <li class="md-nav__item">
    <a href="openj9_support/" title="Supported environments" class="md-nav__link">
      Supported environments
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="openj9_defaults/" title="Default settings" class="md-nav__link">
      Default settings
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="openj9_directories/" title="Directory conventions" class="md-nav__link">
      Directory conventions
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="messages_intro/" title="OpenJ9 messages" class="md-nav__link">
      OpenJ9 messages
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="env_var/" title="Environment variables" class="md-nav__link">
      Environment variables
    </a>
  </li>

        
      </ul>
    </nav>
  </li>

    
  <li class="md-nav__item">
    <a href="legal/" title="Legal" class="md-nav__link">
      Legal
    </a>
  </li>

    
  </ul>
</nav>
                  </div>
                </div>
              </div>
            
            
              <div class="md-sidebar md-sidebar--secondary" data-md-component="toc">
                <div class="md-sidebar__scrollwrap">
                  <div class="md-sidebar__inner">
                    
<nav class="md-nav md-nav--secondary">
  
  
    <label class="md-nav__title" for="toc">On this page ...</label>
    <ul class="md-nav__list" data-md-scrollfix>
      
        <li class="md-nav__item">
  <a href="#what-is-openj9" title="What is OpenJ9" class="md-nav__link">
    What is OpenJ9
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#useful-links" title="Useful links" class="md-nav__link">
    Useful links
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#configuring-your-system" title="Configuring your system" class="md-nav__link">
    Configuring your system
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#performance-tuning" title="Performance tuning" class="md-nav__link">
    Performance tuning
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#runtime-options" title="Runtime options" class="md-nav__link">
    Runtime options
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#default-settings" title="Default settings" class="md-nav__link">
    Default settings
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#supported-environments" title="Supported environments" class="md-nav__link">
    Supported environments
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#troubleshooting" title="Troubleshooting" class="md-nav__link">
    Troubleshooting
  </a>
  
</li>
      
      
    </ul>
  
</nav>
                  </div>
                </div>
              </div>
            
          
          <div class="md-content">
            <article class="md-content__inner md-typeset">
              
<!-- this adds 'pencil' icon to H1 so that you can edit the page directly in GitHub
                
                  <a href="https://github.com/eclipse/openj9-docs/edit/master/docs/index.md" title="Edit this page" class="md-icon md-content__icon">&#xE3C9;</a>
                
-->
                
                <!--
* Copyright (c) 2017, 2018 IBM Corp. and others
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/legal/epl-2.0/ or the Apache
* License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the
* following Secondary Licenses when the conditions for such
* availability set forth in the Eclipse Public License, v. 2.0
* are satisfied: GNU General Public License, version 2 with
* the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH
* Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
-->

<h1 id="eclipse-openj9">Eclipse OpenJ9</h1>
<p>Welcome to the user documentation for the Eclipse OpenJ9 virtual machine (VM).</p>
<p>This user documentation supports the configuration, tuning, and diagnosis of the OpenJ9 VM in an OpenJDK runtime. However, due to differences between the Java SE class libraries, specific options might apply only to one Java SE version. Icons are used to indicate where differences apply. For example:</p>
<p><img alt="Start of content that applies only to Java 8 (LTS)" src="./cr/java8.png" /> This sentence applies only to Java 8 binaries that include the OpenJ9 VM. <img alt="End of content that applies only to Java 8 (LTS)" src="./cr/java_close_lts.png" /></p>
<p><img alt="Start of content that applies only to Java 9 and later" src="./cr/java9plus.png" /> This sentence applies only to Java 9 or later binaries that include the OpenJ9 VM. <img alt="End of content that applies only to Java 9 or later" src="./cr/java_close.png" /></p>
<p><i class="fa fa-pencil-square-o" aria-hidden="true"></i> <strong>Note:</strong> As a usability aid, the icons for long term service (LTS) releases are a different colour from feature releases.</p>
<p>The following table indicates which Java releases are LTS releases and which are feature releases:</p>
<table>
<thead>
<tr>
<th>Java SE version</th>
<th align="center">LTS release</th>
<th align="center">Feature release</th>
</tr>
</thead>
<tbody>
<tr>
<td>8</td>
<td align="center"><i class="fa fa-check" aria-hidden="true"></i><span class="sr-only">yes</span></td>
<td align="center"></td>
</tr>
<tr>
<td>9</td>
<td align="center"></td>
<td align="center"><i class="fa fa-check" aria-hidden="true"></i><span class="sr-only">yes</span></td>
</tr>
<tr>
<td>10</td>
<td align="center"></td>
<td align="center"><i class="fa fa-check" aria-hidden="true"></i><span class="sr-only">yes</span></td>
</tr>
<tr>
<td>11</td>
<td align="center"><i class="fa fa-check" aria-hidden="true"></i><span class="sr-only">yes</span></td>
<td align="center"></td>
</tr>
</tbody>
</table>
<p><i class="fa fa-pencil-square-o" aria-hidden="true"></i> <strong>Note:</strong> Documentation to support OpenJ9 is still under construction. The current content covers
some high level information about OpenJ9 components together with the command-line options and environment variables that you can use to configure the VM when you start your application. We expect further content to be contributed over time. Because OpenJ9 was contributed to the Eclipse Foundation by IBM, this content contains some links to additional information that forms part of the <a href="https://www.ibm.com/support/knowledgecenter/SSYKE2/welcome_javasdk_family.html">IBM&reg; SDK, Java&trade; Technology Edition product documentation</a> in IBM Knowledge Center. That content supplements the documentation here until a more complete set of user documentation is available.</p>
<p>We welcome contributions to the user documentation. If you would like to get involved, please read our <a href="https://github.com/eclipse/openj9-docs/blob/master/CONTRIBUTING.md">Contribution guidelines</a>.</p>
<h2 id="what-is-openj9">What is OpenJ9</h2>
<p>OpenJ9 is a high performance, scalable, Java&trade; virtual machine (VM) implementation that is fully compliant with the <a href="https://docs.oracle.com/javase/specs/index.html">Java Virtual Machine Specification</a>.</p>
<p>At run time, the VM interprets the Java bytecode that is compiled by the Java compiler. The VM acts as a translator between the language and the underlying operating system and hardware. A Java program requires a specific VM to run on a particular platform, such as Linux&trade;, z/OS&reg;, or Windows&trade;.</p>
<p>This reference material provides information about the VM configuration and tuning options, together with the default settings.</p>
<h2 id="useful-links">Useful links</h2>
<ul>
<li><a href="https://www.eclipse.org/openj9">Eclipse OpenJ9 website home page</a></li>
<li><a href="https://github.com/eclipse/openj9">Eclipse OpenJ9 GitHub repository</a></li>
<li><a href="https://projects.eclipse.org/projects/technology.openj9">Eclipse Foundation OpenJ9 project page</a></li>
</ul>
<p>You can obtain pre-built OpenJDK binaries from the AdoptOpenJDK project:</p>
<ul>
<li><a href="https://adoptopenjdk.net/releases.html?variant=openjdk8&amp;jvmVariant=openj9">OpenJDK8 with OpenJ9</a></li>
<li><a href="https://adoptopenjdk.net/releases.html?variant=openjdk9&amp;jvmVariant=openj9">OpenJDK9 with OpenJ9</a></li>
<li><a href="https://adoptopenjdk.net/releases.html?variant=openjdk10&amp;jvmVariant=openj9">OpenJDK10 with OpenJ9</a></li>
</ul>
<h2 id="configuring-your-system">Configuring your system</h2>
<p>For normal operation, certain environment variables must be set at the operating system level. Depending on your system environment, you might also want to set other configuration options that allow the VM to exploit hardware and operating system features. Read <a href="https://www.ibm.com/support/knowledgecenter/SSYKE2_8.0.0/com.ibm.java.vm.80.doc/docs/j9_configure.html">Customizing your system</a> to learn more about the following options:</p>
<ul>
<li>Setting the PATH and CLASSPATH environment variable.</li>
<li>Setting the LIBPATH or LD_LIBRARY_PATH environment variable (AIX&reg; and Linux).</li>
<li>Setting ulimits on AIX and Linux systems to ensure that the operating system allocates sufficient resources for your application.</li>
<li>Setting region size, BPXPRM parameters, and Language Environment&reg; runtime options on z/OS systems.</li>
<li>If your application allocates a large amount of memory and frequently accesses that memory, you might want to enable large page support on your system. See <a href="https://www.ibm.com/support/knowledgecenter/SSYKE2_8.0.0/com.ibm.java.vm.80.doc/docs/j9_configure_large_page.html">Configuring large page memory allocation</a>.</li>
<li>Configuring Dynamic LPAR support on AIX systems.</li>
</ul>
<h2 id="performance-tuning">Performance tuning</h2>
<p>OpenJ9 is configured to start with a set of default options that provide the optimal runtime environment for Java applications with typical workloads. However, if your application is atypical, you can improve performance by tuning the OpenJ9 VM. You can also improve performance by enabling hardware features or using specific APIs in your application code. Click the links to learn more about the following options:</p>
<dl>
<dt>Choosing a garbage collection policy</dt>
<dd>J9 includes several garbage collection policies. To learn more about these policies and the types of application workload that can benefit from them, see <a href="gc/">Garbage Collection</a>.</dd>
<dt>Improving startup times with class data sharing</dt>
<dd>You can share class data between running VMs, which can reduce the startup time for a VM once the cache has been created. For more information, see <a href="shrc/">Class Data Sharing</a>.</dd>
</dl>
<!-- These features not yet available in OpenJDK class libaries

Using hardware compression acceleration devices
: J9 can exploit hardware compression devices to reduce CPU consumption and shorten processing times.
- For AIX and Linux systems, see Enabling hardware compression acceleration.
- For IBM zEnterprise<sup>&reg;</sup> systems, see zEnterprise Data Compression.

Exploiting Remote Direct Memory Access (RDMA)
: High performance network infrastructure that supports Remote Direct Memory Access (RDMA) is designed to speed up communications between applications. : On Linux systems, existing Java socket applications can take advantage of RDMA-capable network adapters by using extensions to the Socket and ServerSocket APIs. For more information, see Java Sockets over Remote Direct Memory Access. Alternatively, you can write applications that use APIs in the jVerbs library to communicate directly over RDMA-capable infrastructure. See The jVerbs library.
-  On z/OS systems, J9 supports the use of the SMC-R protocol solution to enable TCP socket applications to transparently use RDMA. For more information, see Shared Memory Communication via RDMA.

Exploiting Graphics Processing Units (GPU)
: On Linux and Windows systems, you can improve the performance of your Java applications by offloading certain processing functions from your processor (CPU) to a graphics processing unit. For more information, see Exploiting Graphics Processing Units.-->

<dl>
<dt>Dealing with native data</dt>
<dd>If your Java application manipulates native data, consider writing your application to take advantage of methods in the Data Access Accelerator API.</dd>
<dt>Optimizing your application for cloud deployments</dt>
<dd>To improve the performance of applications that run in the cloud, try setting the following tuning options:</dd>
</dl>
<ul>
<li>Use a shared classes cache (<code>-Xshareclasses -XX:SharedCacheHardLimit=200m -Xscmx60m</code>) with Ahead-Of-Time (AOT) compilation to improve your startup time. For more information, see <a href="shrc/">Class Data Sharing</a> and <a href="aot/">AOT Compiler</a>.</li>
<li>Use the idle VM settings to maintain a smaller footprint, which can generate cost savings for cloud services that charge based on memory usage. The idle tuning mechanism detects when the VM is idle, releasing free memory pages to keep the footprint as small as possible and keep your running costs to a minimum. For more information, see <a href="xxidletuningminidlewaittime/">-XX:IdleTuningMinIdleWaitTime</a>.</li>
<li>Use the <a href="./xtunevirtualized">-Xtune:virtualized</a> option, which configures OpenJ9 for typical cloud deployments where VM guests are provisioned with a small number of virtual CPUs to maximize the number of applications that can be run. When enabled, OpenJ9 adapts its internal processes to reduce the amount of CPU consumed and trim down the memory footprint. These changes come at the expense of only a small loss in throughput.</li>
</ul>
<h2 id="runtime-options">Runtime options</h2>
<p>Runtime options are specified on the command line and include system properties, standard options, nonstandard (<strong>-X</strong>) options, and <strong>-XX</strong> options. For a detailed list of runtime options, see <a href="cmdline_specifying/">OpenJ9 command-line options</a></p>
<h2 id="default-settings">Default settings</h2>
<p>If you do not specify any options on the command line at run time, the OpenJ9 VM starts with default settings that define how it operates. For more information about these settings, see <a href="openj9_defaults/">Default settings for the OpenJ9 VM</a>.</p>
<h2 id="supported-environments">Supported environments</h2>
<p>OpenJDK binaries that contain the OpenJ9 VM are supported on a range of hardware and operating systems. This range is expanding as work progresses at the Eclipse foundation. See the <a href="openj9_support/">current list of supported environments</a> for details.</p>
<p><i class="fa fa-pencil-square-o" aria-hidden="true"></i> <strong>Note:</strong> This user guide contains information about configuring, tuning, and debugging OpenJ9 on the z/OS&reg; platform. This content was contributed by IBM so that it is available when the work to create OpenJDK binaries for the z/OS platform is complete.</p>
<h2 id="troubleshooting">Troubleshooting</h2>
<p>The OpenJ9 diagnostic component contains extensive features to assist with problem determination. Diagnostic data is produced under default conditions, but can also be controlled by starting the VM with the <a href="xdump/">-Xdump option</a> or using the <code>com.ibm.jvm.Dump</code> API. You can also trace Java applications, methods, and VM operations by using the <a href="xtrace/">-Xtrace option</a>.</p>
<p>To get started, read <a href="diag_overview/">Diagnostic tools and data</a>.</p>
<!-- ==== END OF TOPIC ==== index.md ==== -->
                
                  
<!--
              
                
-->
              <!-- This block was originally in the theme's 'footer.html' partial file. It has been moved here in part to resolve issues with the footer being too large. -->
              
                <!--
* Copyright (c) 2017, 2018 IBM Corp. and others
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/legal/epl-2.0/ or the Apache
* License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the
* following Secondary Licenses when the conditions for such
* availability set forth in the Eclipse Public License, v. 2.0
* are satisfied: GNU General Public License, version 2 with
* the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH
* Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
-->
              
                <div class="md-footer-nav">
                  <nav class="md-footer-nav__inner md-grid">
                    <!-- Separator -->
                    <img alt="" src="../cr/rule.png">
                    
                    
                      <a href="version0.9/" title="Version 0.9.0" class="md-flex md-footer-nav__link md-footer-nav__link--next" rel="next">
                        <div class="md-flex__cell md-flex__cell--stretch md-footer-nav__title">
                          <span class="md-flex__ellipsis">
                            <span class="md-footer-nav__direction">
                              Next
                            </span>
                            Version 0.9.0
                          </span>
                        </div>
                        <div class="md-flex__cell md-flex__cell--shrink">
                          <i class="md-icon md-icon--arrow-forward md-footer-nav__button"></i>
                        </div>
                      </a>
                    
                  </nav>
                </div>
              
              
            </article>
          </div>
        </div>
      </main>
      
        <!--
* Copyright (c) 2017, 2018 IBM Corp. and others
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/legal/epl-2.0/ or the Apache
* License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the
* following Secondary Licenses when the conditions for such
* availability set forth in the Eclipse Public License, v. 2.0
* are satisfied: GNU General Public License, version 2 with
* the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH
* Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
-->
<cite></cite>
<footer class="md-footer">

  <div class="md-footer-meta md-typeset">
    

      <!--
* Copyright (c) 2017, 2018 IBM Corp. and others
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/legal/epl-2.0/ or the Apache
* License, Version 2.0 which accompanies this distribution and
* is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the
* following Secondary Licenses when the conditions for such
* availability set forth in the Eclipse Public License, v. 2.0
* are satisfied: GNU General Public License, version 2 with
* the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH
* Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
-->

  <div class="md-footer-social1">
    
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
    
      <a href="https://github.com/eclipse/openj9" class="md-footer-social__link fa fa-github"></a>
    
      <a href="https://openj9.slack.com" class="md-footer-social__link fa fa-slack"></a>
    
      <a href="https://twitter.com/openj9" class="md-footer-social__link fa fa-twitter"></a>
    
      <a href="https://stackoverflow.com/search?q=OpenJ9" class="md-footer-social__link fa fa-stack-overflow"></a>
    
  </div>

    
    <div class="md-footer-eclipse1">OpenJ9 is an Eclipse Incubator project.</div>

    <div class="md-footer-links1">
      <span class="no-wrap"><i class="fa fa-chevron-circle-right f_mini" aria-hidden="true"></i><a class="dark-link" href="http://www.eclipse.org">Eclipse Foundation website</a></span>
      &nbsp; <span class="no-wrap"><i class="fa fa-chevron-circle-right f_mini" aria-hidden="true"></i><a class="dark-link" href="http://www.eclipse.org/legal/privacy.php">Privacy policy</a></span>
      &nbsp; <span class="no-wrap"><i class="fa fa-chevron-circle-right f_mini" aria-hidden="true"></i><a class="dark-link" href="http://www.eclipse.org/legal/termsofuse.php">Website terms of use</a></span>
      &nbsp; <span class="no-wrap"><i class="fa fa-chevron-circle-right f_mini" aria-hidden="true"></i><a class="dark-link" href="http://www.eclipse.org/legal/copyright.php">Copyright agent</a></span>
      &nbsp; <span class="no-wrap"><i class="fa fa-chevron-circle-right f_mini" aria-hidden="true"></i><a class="dark-link" href="http://www.eclipse.org/legal">Legal</a></span>
    </div>

    <div class="md-footer-power1">
      powered by
      <a href="http://www.mkdocs.org" title="MkDocs">MkDocs</a>
      and
      <a href="http://squidfunk.github.io/mkdocs-material/" title="Material for MkDocs">
      Material for MkDocs</a><br/><br/>
    </div>

  </div>

</footer>
      
    </div>
    
      <script src="./assets/javascripts/application.abd7b172.js"></script>
      
        
      <script>app.initialize({version:"0.17.2",url:{base:"."}})</script>
      
    
  </body>
</html>