<command>CHECKPOINT</command>.
    </para>
    <para>
     For more information, see
     <xref linkend="wal-configuration"/>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-checkpointer">
   <glossterm>Checkpointer (process)</glossterm>
   <glossdef>
    <para>
     An <glossterm linkend="glossary-auxiliary-proc">auxiliary process</glossterm>
     that is responsible for executing
     <glossterm linkend="glossary-checkpoint">checkpoints</glossterm>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry>
   <glossterm>Class (archaic)</glossterm>
   <glosssee otherterm="glossary-relation" />
  </glossentry>

  <glossentry id="glossary-client">
   <glossterm>Client (process)</glossterm>
   <glossdef>
    <para>
     Any process, possibly remote, that establishes a
     <glossterm linkend="glossary-session">session</glossterm>
     by <glossterm linkend="glossary-connection">connecting</glossterm> to an
     <glossterm linkend="glossary-instance">instance</glossterm>
     to interact with a <glossterm linkend="glossary-database">database</glossterm>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-cluster-owner">
   <glossterm>Cluster owner</glossterm>
   <glossdef>
    <para>
     The operating system user that owns the
     <glossterm linkend="glossary-data-directory">data directory</glossterm>
     and under which the <literal>postgres</literal> process is run.
     It is required that this user exist prior to creating a new
     <glossterm linkend="glossary-db-cluster">database cluster</glossterm>.
    </para>
    <para>
     On operating systems with a <literal>root</literal> user,
     said user is not allowed to be the cluster owner.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-column">
   <glossterm>Column</glossterm>
   <glossdef>
    <para>
     An <glossterm linkend="glossary-attribute">attribute</glossterm> found in
     a <glossterm linkend="glossary-table">table</glossterm> or
     <glossterm linkend="glossary-view">view</glossterm>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-commit">
   <glossterm>Commit</glossterm>
   <glossdef>
    <para>
     The act of finalizing a
     <glossterm linkend="glossary-transaction">transaction</glossterm> within
     the <glossterm linkend="glossary-database">database</glossterm>, which
     makes it visible to other transactions and assures its
     <glossterm linkend="glossary-durability">durability</glossterm>.
    </para>
    <para>
     For more information, see
     <xref linkend="sql-commit"/>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-concurrency">
   <glossterm>Concurrency</glossterm>
   <glossdef>
    <para>
     The concept that multiple independent operations happen within the
     <glossterm linkend="glossary-database">database</glossterm> at the same time.
     In <productname>PostgreSQL</productname>, concurrency is controlled by
     the <glossterm linkend="glossary-mvcc">multiversion concurrency control</glossterm>
     mechanism.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-connection">
   <glossterm>Connection</glossterm>
   <glossdef>
    <para>
     An established line of communication between a client process and a
     <glossterm linkend="glossary-backend">backend</glossterm> process,
     usually over a network, supporting a
     <glossterm linkend="glossary-session">session</glossterm>.  This term is
     sometimes used as a synonym for session.
    </para>
    <para>
     For more information, see
     <xref linkend="runtime-config-connection"/>.
    </para>
   </glossdef>
  </glossentry>

  <glossentry id="glossary-consistency">
   <glossterm>Consistency</glossterm>
   <glossdef>
    <para>
     The property that the data in the
     <glossterm linkend="glossary-database">database</glossterm>
     is always in compliance with
     <glossterm linkend="glossary-constraint">integrity constraints</glossterm>.