streaming replication mode, where
             a small set of replication commands can be issued
             instead of SQL statements. Value can be
             <literal>true</literal>, <literal>false</literal>, or
             <literal>database</literal>, and the default is
             <literal>false</literal>. See
             <xref linkend="protocol-replication"/> for details.
            </para>
           </listitem>
          </varlistentry>
         </variablelist>

         In addition to the above, other parameters may be listed.
         Parameter names beginning with <literal>_pq_.</literal> are
         reserved for use as protocol extensions, while others are
         treated as run-time parameters to be set at backend start
         time.  Such settings will be applied during backend start
         (after parsing the command-line arguments if any) and will
         act as session defaults.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term>String</term>
       <listitem>
        <para>
         The parameter value.
        </para>
       </listitem>
      </varlistentry>
     </variablelist>
    </listitem>
   </varlistentry>

   <varlistentry id="protocol-message-formats-Sync">
    <term>Sync (F)</term>
    <listitem>
     <variablelist>
      <varlistentry>
       <term>Byte1('S')</term>
       <listitem>
        <para>
         Identifies the message as a Sync command.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term>Int32(4)</term>
       <listitem>
        <para>
         Length of message contents in bytes, including self.
        </para>
       </listitem>
      </varlistentry>
     </variablelist>
    </listitem>
   </varlistentry>

   <varlistentry id="protocol-message-formats-Terminate">
    <term>Terminate (F)</term>
    <listitem>
     <variablelist>
      <varlistentry>
       <term>Byte1('X')</term>
       <listitem>
        <para>
         Identifies the message as a termination.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term>Int32(4)</term>
       <listitem>
        <para>
         Length of message contents in bytes, including self.
        </para>
       </listitem>
      </varlistentry>
     </variablelist>
    </listitem>
   </varlistentry>
  </variablelist>
 </sect1>

 <sect1 id="protocol-error-fields">
  <title>Error and Notice Message Fields</title>

  <para>
   This section describes the fields that can appear in ErrorResponse and
   NoticeResponse messages.  Each field type has a single-byte identification
   token.  Note that any given field type should appear at most once per
   message.
  </para>

  <variablelist>
   <varlistentry>
    <term><literal>S</literal></term>
    <listitem>
     <para>
      Severity: the field contents are
      <literal>ERROR</literal>, <literal>FATAL</literal>, or
      <literal>PANIC</literal> (in an error message), or
      <literal>WARNING</literal>, <literal>NOTICE</literal>, <literal>DEBUG</literal>,
      <literal>INFO</literal>, or <literal>LOG</literal> (in a notice message),
      or a localized translation of one of these.  Always present.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>V</literal></term>
    <listitem>
     <para>
      Severity: the field contents are
      <literal>ERROR</literal>, <literal>FATAL</literal>, or
      <literal>PANIC</literal> (in an error message), or
      <literal>WARNING</literal>, <literal>NOTICE</literal>, <literal>DEBUG</literal>,
      <literal>INFO</literal>, or <literal>LOG</literal> (in a notice message).
      This is identical to the <literal>S</literal> field except
      that the contents are never localized.  This is present only in
      messages generated by <productname>PostgreSQL</productname> versions 9.6
      and later.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>C</literal></term>