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  <info>
    <title>Terminology</title>
  </info>

  <para></para>

  <section>
    <info>
      <title>Server or JOnAS instance</title>
    </info>

    <para>A server, or JOnAS instance, is a java process started via the
    <emphasis>jonas start</emphasis> command, or via the administration tool <xi:include
    href="variables.xml" xpointer="element(/1/7/1)" />.</para>

    <para>Several servers may run on the same physical host.</para>
  </section>

  <section>
    <info>
      <title>Service</title>
    </info>

    <para>When a server starts, services are started.</para>

    <para>A service typically provides system resources to containers. Most of
    the components of the <xi:include href="variables.xml"
    xpointer="element(appserver)" /> application server are pre-defined
    services. However, it is possible and easy for an advanced user to define
    a new service and to integrate it into <xi:include href="variables.xml"
    xpointer="element(appserver)" />.</para>

    <para><xi:include href="variables.xml" xpointer="element(appserver)" />
    services are manageable through JMX.</para>
  </section>

  <section>
    <info>
      <title>Container</title>
    </info>

    <para>A container consists of a set of Java classes that implement the
    <xi:include href="variables.xml" xpointer="element(j2ee)" />
    specification. The role of the container is to provide the facilities for
    executing <xi:include href="variables.xml" xpointer="element(j2ee)" />
    components.</para>

    <para>There are three types of containers:</para>

    <itemizedlist>
      <listitem>
        <para>EJB container in which Enterprise JavaBeans are deployed and
        run</para>
      </listitem>

      <listitem>
        <para>Web container for JSPs and servlets</para>
      </listitem>

      <listitem>
        <para>Client container</para>
      </listitem>
    </itemizedlist>
  </section>

  <section>
    <info>
      <title>Domain</title>
    </info>

    <para>A domain represents an administration perimeter which is under the
    control of an administration authority.</para>

    <para>This perimeter contains management targets like servers and
    clusters.</para>

    <para>If a domain contains several elements, it provides at least one
    common administration point represented by a master server.</para>
  </section>

  <section>
    <info>
      <title>Master server</title>
    </info>

    <para>A master is a <xi:include href="variables.xml"
    xpointer="appserver" /> instance having particular management capabilities
    within the domain:</para>

    <itemizedlist>
      <listitem>
        <para>it is aware of the domain's topology</para>
      </listitem>

      <listitem>
        <para>it allows management and monitoring of all the elements
        belonging to the domain</para>
      </listitem>
    </itemizedlist>
  </section>

  <section>
    <info>
      <title>Cluster</title>
    </info>

    <para>A cluster is a group of JOnAS servers having common properties within a domain. It usually allows to run a
    J2EE application, or a J2EE module, on the cluster members as if they were
    a single server. The objective is to achieve applications scalability and
    high availability.</para>

    <para>JOnAS supports several cluster types:</para>

    <itemizedlist>
      <listitem>
        <para>Clusters for Web level load-balancing</para>
      </listitem>

      <listitem>
        <para>Clusters for high availability of Web components</para>
      </listitem>

      <listitem>
        <para>Clusters for EJB level load-balancing</para>
      </listitem>

      <listitem>
        <para>Clusters for high availability of EJB components</para>
      </listitem>

      <listitem>
        <para>Clusters for JMS destination scalability and high
        availability</para>
      </listitem>

      <listitem>
        <para>Clusters for administration purpose which facilitate management
        operations like deployment /undeployment.</para>
      </listitem>
    </itemizedlist>

    <para>From the administrator point of view, a cluster represents a single
    administration target.</para>

    <para>Note that a particular <xi:include href="variables.xml"
    xpointer="element(appserver)" /> server may belong to zero, one or more
    clusters.</para>
  </section>
</section>
