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      -Djdk.nativeCrypto
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      -Djdk.nativeGCM
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      -Xcomp
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      -Xcompactexplicitgc
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      -Xconcurrentlevel
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      -Xconcurrentslack
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      -Xconmeter
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      -Xdisableexcessivegc
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  <li class="md-nav__item">
    <a href="../xenableexplicitgc/" title="-Xdisableexplicitgc" class="md-nav__link">
      -Xdisableexplicitgc
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      -Xdisablejavadump
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      -Xdisablestringconstantgc
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      -Xdump
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      -Xenableexcessivegc
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      -Xenableexplicitgc
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      -Xfuture
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      -Xgc
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      -Xgc:splitheap
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      -Xgcpolicy
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      -Xgcthreads
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      -Xifa
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      -Xint
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      -Xiss
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      -Xjit
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      -Xjni
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      -Xlinenumbers
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      -Xloa
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      -Xloainitial
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      -Xloamaximum
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      -Xloaminimum
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      -XlockReservation
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      -Xlockword
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      -Xlp
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  <li class="md-nav__item">
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      -Xlp:codecache
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  <li class="md-nav__item">
    <a href="../xlpobjectheap/" title="-Xlp:objectheap" class="md-nav__link">
      -Xlp:objectheap
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      -Xmaxe
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      -Xmaxt
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      -Xmca
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      -Xmco
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      -Xmcrs
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      -Xmine
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      -Xminf
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  <li class="md-nav__item">
    <a href="../xmint/" title="-Xmint" class="md-nav__link">
      -Xmint
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      -Xmn
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    <a href="../xmn/" title="-Xmns" class="md-nav__link">
      -Xmns
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      -Xmnx
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      -Xmo
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      -Xmoi
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  <li class="md-nav__item">
    <a href="../xmo/" title="-Xmos" class="md-nav__link">
      -Xmos
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  <li class="md-nav__item">
    <a href="../xmo/" title="-Xmox" class="md-nav__link">
      -Xmox
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    <a href="../xmr/" title="-Xmr" class="md-nav__link">
      -Xmr
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  <li class="md-nav__item">
    <a href="../xmr/" title="-Xmrx" class="md-nav__link">
      -Xmrx
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      -Xms
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<nav class="md-nav md-nav--secondary">
  
  
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      -Xnoaot
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  <li class="md-nav__item">
    <a href="../xclassgc/" title="-Xnoclassgc" class="md-nav__link">
      -Xnoclassgc
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  <li class="md-nav__item">
    <a href="../xcompactexplicitgc/" title="-Xnocompactexplicitgc" class="md-nav__link">
      -Xnocompactexplicitgc
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  </li>

        
  <li class="md-nav__item">
    <a href="../xcompactgc/" title="-Xnocompactgc" class="md-nav__link">
      -Xnocompactgc
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  <li class="md-nav__item">
    <a href="../xcompressedrefs/" title="-Xnocompressedrefs" class="md-nav__link">
      -Xnocompressedrefs
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  <li class="md-nav__item">
    <a href="../xjit/" title="-Xnojit" class="md-nav__link">
      -Xnojit
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      -Xnolinenumbers
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  <li class="md-nav__item">
    <a href="../xloa/" title="-Xnoloa" class="md-nav__link">
      -Xnoloa
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    <a href="../xsigcatch/" title="-Xnosigcatch" class="md-nav__link">
      -Xnosigcatch
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  <li class="md-nav__item">
    <a href="../xsigchain/" title="-Xnosigchain" class="md-nav__link">
      -Xnosigchain
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    <a href="../xnumanone/" title="-Xnuma:none" class="md-nav__link">
      -Xnuma:none
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  <li class="md-nav__item">
    <a href="../xoptionsfile/" title="-Xoptionsfile" class="md-nav__link">
      -Xoptionsfile
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      -Xquickstart
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  <li class="md-nav__item">
    <a href="../xrs/" title="-Xrs" class="md-nav__link">
      -Xrs
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  <li class="md-nav__item">
    <a href="../xsamplingexpirationtime/" title="-XsamplingExpirationTime" class="md-nav__link">
      -XsamplingExpirationTime
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      -Xscdmx
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      -Xscmaxaot
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    <a href="../xscminjitdata/" title="-Xscmaxjitdata" class="md-nav__link">
      -Xscmaxjitdata
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    <a href="../xscminaot/" title="-Xscminaot" class="md-nav__link">
      -Xscminaot
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      -Xscminjitdata
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    <a href="../xscmx/" title="-Xscmx" class="md-nav__link">
      -Xscmx
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      -Xshareclasses
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      -Xsigcatch
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      -Xsigchain
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<h1 id="-xms-xmx">-Xms / -Xmx</h1>
<p>These Oracle&reg; HotSpot&trade; options set the initial/minimum Java&trade; heap size, and the maximum heap size respectively. These options are recognized by the OpenJ9 VM.</p>
<p><i class="fa fa-pencil-square-o" aria-hidden="true"></i> <strong>Notes:</strong></p>
<ul>
<li>If you set <code>-Xms</code> &gt; <code>-Xmx</code>, the OpenJ9 VM fails with the message <code>-Xms too large for -Xmx</code>.</li>
<li>If you exceed the limit set by the <code>-Xmx</code> option, the OpenJ9 VM generates an <code>OutofMemoryError</code>.</li>
</ul>
<p>If you are allocating the Java heap with large pages, see also <a href="../xlp/">-Xlp</a> and
<a href="https://www.ibm.com/support/knowledgecenter/SSYKE2_8.0.0/com.ibm.java.vm.80.doc/docs/mm_gc_compressed_refs.html">More effective heap usage using compressed references</a>.</p>
<p>You can also use the <a href="../xmo/"><code>-Xmo</code></a> option (not supported by the balanced garbage collection policy):<br />
If the scavenger is enabled, <code>-Xms</code> &ge; <code>-Xmn</code> + <code>-Xmo</code><br />
If the scavenger is disabled, <code>-Xms</code> &ge; <code>-Xmo</code>  </p>
<h2 id="syntax">Syntax</h2>
<table>
<thead>
<tr>
<th>Setting</th>
<th>Effect</th>
<th>Default</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>-Xms&lt;size&gt;</code></td>
<td>Set initial heap size</td>
<td>8 MB</td>
</tr>
<tr>
<td><code>-Xmx&lt;size&gt;</code></td>
<td>Set maximum heap size</td>
<td>25% of available memory (25 GB maximum)</td>
</tr>
</tbody>
</table>
<p>See <a href="../x_jvm_commands/">Using -X command-line options</a> for more information about the <code>&lt;size&gt;</code> parameter.<br />
See <a href="../openj9_defaults/">Default settings for the OpenJ9 VM</a> for more about default values.</p>
<h2 id="examples">Examples</h2>
<dl>
<dt><code>-Xms2m -Xmx64m</code></dt>
<dd>Heap starts at 2 MB and grows to a maximum of 64 MB.</dd>
<dt><code>-Xms100m -Xmx100m</code></dt>
<dd>Heap starts at 100 MB and never grows.</dd>
<dt><code>-Xms50m</code></dt>
<dd>Heap starts at 50 MB and grows to the default maximum.</dd>
<dt><code>-Xmx256m</code></dt>
<dd>Heap starts at default initial value and grows to a maximum of 256 MB.</dd>
</dl>
<h2 id="see-also">See also</h2>
<ul>
<li><a href="../xsoftmx/">-Xsoftmx (Set "soft" maximum Java heap size)</a></li>
</ul>
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