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<appendix id="Java-Broker-Appendix-Environment-Variables">
  <title>Environment Variables</title>
  <para>The following table describes the environment variables understood by the Qpid scripts
    contained within the <literal>/bin</literal> directory within the Broker distribution.</para>
  <para>To take effect, these variables must be set within the shell (and exported - if using Unix)
    before invoking the script.</para>
  <table pgwide="1">
    <title>Environment variables</title>
    <tgroup cols="3">
      <thead>
        <row>
          <entry>Environment variable</entry>
          <entry>Default</entry>
          <entry>Purpose</entry>
        </row>
      </thead>
      <tbody>
        <row id="Java-Broker-Appendix-Environment-Variables-Qpid-Home">
          <entry>QPID_HOME</entry>
          <entry>
            <para>None</para>
          </entry>
          <entry>
            <para>The variable used to tell the Broker its installation directory. It must be an
              absolute path. This is used to determine the location of Qpid's dependency JARs and
              some configuration files.</para>
            <para>Typically the value of this variable will look similar to
                <literal>c:\qpid\&windowsExtractedBrokerDirName;</literal> (Windows) or
                <literal>/usr/local/qpid/&unixExtractedBrokerDirName;</literal> (Unix). The
              installation prefix will differ from installation to installation. </para>
            <para>If not set, a value for <literal>QPID_HOME</literal> is derived from the location
              of the script itself.</para>
          </entry>
        </row>
        <row id="Java-Broker-Appendix-Environment-Variables-Qpid-Work">
          <entry>QPID_WORK</entry>
          <entry>
            <para>User's home directory</para>
          </entry>
          <entry>
            <para>Used as the default root directory for any data written by the Broker. This is the
              default location for any message data written to persistent stores and the Broker's
              log file.</para>
            <para>For example, <literal>QPID_WORK=/var/qpidwork</literal>.</para>
          </entry>
        </row>
        <row id="Java-Broker-Appendix-Environment-Variables-Qpid-Opts">
          <entry>QPID_OPTS</entry>
          <entry>
            <para>None</para>
          </entry>
          <entry>
            <para>This is the preferred mechanism for passing Java <link
                linkend="Java-Broker-Appendix-System-Properties">system properties</link> to the
              Broker. The value must be a list of system properties each separate by a space.
                  <literal>-D<replaceable>name1</replaceable>=<replaceable>value1</replaceable>
                  -D<replaceable>name2</replaceable>=<replaceable>value2</replaceable></literal>.
            </para>
          </entry>
        </row>
        <row id="Java-Broker-Appendix-Environment-Variables-Qpid-Java-Gc">
          <entry>QPID_JAVA_GC</entry>
          <entry>
            <literal>-XX:+HeapDumpOnOutOfMemoryError -XX:+UseConcMarkSweepGC</literal>
          </entry>
          <entry>
            <para>This is the preferred mechanism for customising garbage collection behaviour. The
              value should contain valid garbage collection options(s) for the target JVM.</para>
            <para>Refer to the JVM's documentation for details.</para>
          </entry>
        </row>
        <row id="Java-Broker-Appendix-Environment-Variables-Qpid-Java-Mem">
          <entry>QPID_JAVA_MEM</entry>
          <entry>
            <literal>-Xmx1024m</literal>
          </entry>
          <entry>
            <para>This is the preferred mechanism for customising the size of the JVM's heap memory.
              The value should contain valid memory option(s) for the target JVM. Oracle JVMs
              understand <literal>-Xmx</literal> to specify a maximum heap size and
                <literal>-Xms</literal> an initial size.</para>
            <para>For example, <code>QPID_JAVA_MEM=-Xmx6g</code> would set a maximum heap size of
              6GB.</para>
            <para>Refer to the JVM's documentation for details.</para>
          </entry>
        </row>
        <row id="Java-Broker-Appendix-Environment-Variables-Java-Opts">
          <entry>JAVA_OPTS</entry>
          <entry>None</entry>
          <entry>
            <para>This is the preferred mechanism for passing any other JVM options. This variable is
              commonly used to pass options for diagnostic purposes, for instance to turn on verbose
              GC. <literal>-verbose:gc</literal>.</para>
            <para>Refer to the JVM's documentation for details.</para>
          </entry>
        </row>
      </tbody>
    </tgroup>
  </table>
</appendix>
