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      Switching to OpenJ9
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  <li class="md-nav__item md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-12-4" type="checkbox" id="nav-12-4">
    
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      System property options
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    <nav class="md-nav" data-md-component="collapsible" data-md-level="2">
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        System property options
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  <li class="md-nav__item">
    <a href="../d_jvm_commands/" title="Using System properties" class="md-nav__link">
      Using System properties
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  <li class="md-nav__item">
    <a href="../dcomibmenableclasscaching/" title="-Dcom.ibm.enableClassCaching" class="md-nav__link">
      -Dcom.ibm.enableClassCaching
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  </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
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  </li>

        
  <li class="md-nav__item">
    <a href="../dcomibmgpudisable/" title="-Dcom.ibm.gpu.disable" class="md-nav__link">
      -Dcom.ibm.gpu.disable
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../dcomibmgpuenable/" title="-Dcom.ibm.gpu.enable" class="md-nav__link">
      -Dcom.ibm.gpu.enable
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../dcomibmgpuverbose/" title="-Dcom.ibm.gpu.verbose" class="md-nav__link">
      -Dcom.ibm.gpu.verbose
    </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>

        
  <li class="md-nav__item">
    <a href="../djavalangstringsubstringnocopy/" title="-Djava.lang.string.substring.nocopy" class="md-nav__link">
      -Djava.lang.string.substring.nocopy
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djavalangstringbuffergrowaggressively/" title="-Djava.lang.stringBuffer.growAggressively" class="md-nav__link">
      -Djava.lang.stringBuffer.growAggressively
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djdknativecbc/" title="-Djdk.nativeCBC" class="md-nav__link">
      -Djdk.nativeCBC
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djdknativechacha20/" title="-Djdk.nativeChaCha20" class="md-nav__link">
      -Djdk.nativeChaCha20
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djdknativecrypto/" title="-Djdk.nativeCrypto" class="md-nav__link">
      -Djdk.nativeCrypto
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djdknativedigest/" title="-Djdk.nativeDigest" class="md-nav__link">
      -Djdk.nativeDigest
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djdknativegcm/" title="-Djdk.nativeGCM" class="md-nav__link">
      -Djdk.nativeGCM
    </a>
  </li>

        
  <li class="md-nav__item">
    <a href="../djdknativersa/" title="-Djdk.nativeRSA" class="md-nav__link">
      -Djdk.nativeRSA
    </a>
  </li>

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

        
  <li class="md-nav__item md-nav__item--active md-nav__item--nested">
    
      <input class="md-toggle md-nav__toggle" data-md-toggle="nav-12-5" type="checkbox" id="nav-12-5" checked>
    
    <label class="md-nav__link" for="nav-12-5">
      JVM -X options
    </label>
    <nav class="md-nav" data-md-component="collapsible" data-md-level="2">
      <label class="md-nav__title" for="nav-12-5">
        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 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">
        -Xconcurrentbackground
      </label>
    
    <a href="./" title="-Xconcurrentbackground" class="md-nav__link md-nav__link--active">
      -Xconcurrentbackground
    </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="#syntax" class="md-nav__link">
    Syntax
  </a>
  
</li>
      
        <li class="md-nav__item">
  <a href="#default-behavior" class="md-nav__link">
    Default behavior
  </a>
  
</li>
      
      
    </ul>
  
</nav>
    
  </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="../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="../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="../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>
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<h1 id="-xconcurrentbackground">-Xconcurrentbackground</h1>
<p>Specifies the number of low-priority background threads attached to assist the mutator threads in concurrent mark.</p>
<h2 id="syntax">Syntax</h2>
<pre><code>    -Xconcurrentbackground&lt;n&gt;
</code></pre>
<h2 id="default-behavior">Default behavior</h2>
<p>The default is <code>0</code> for Linux&reg; on IBM Z&reg; and <code>1</code> on all other platforms.</p>
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