</para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>error</structfield> <type>text</type>
      </para>
      <para>
       If not null, an error message indicating why this entry could
       not be applied
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   If the configuration file contains syntax errors or invalid parameter
   names, the server will not attempt to apply any settings from it, and
   therefore all the <structfield>applied</structfield> fields will read as false.
   In such a case there will be one or more rows with
   non-null <structfield>error</structfield> fields indicating the
   problem(s).  Otherwise, individual settings will be applied if possible.
   If an individual setting cannot be applied (e.g., invalid value, or the
   setting cannot be changed after server start) it will have an appropriate
   message in the <structfield>error</structfield> field.  Another way that
   an entry might have <structfield>applied</structfield> = false is that it is
   overridden by a later entry for the same parameter name; this case is not
   considered an error so nothing appears in
   the <structfield>error</structfield> field.
  </para>

  <para>
   See <xref linkend="config-setting"/> for more information about the various
   ways to change run-time parameters.
  </para>

</sect1>

 <sect1 id="view-pg-group">
  <title><structname>pg_group</structname></title>

  <indexterm zone="view-pg-group">
   <primary>pg_group</primary>
  </indexterm>

  <!-- Unlike information_schema.applicable_roles, this shows no members for
       pg_database_owner.  The v8.1 catalog would have shown no members if
       that role had existed at the time. -->
  <para>
   The view <structname>pg_group</structname> exists for backwards
   compatibility: it emulates a catalog that existed in
   <productname>PostgreSQL</productname> before version 8.1.
   It shows the names and members of all roles that are marked as not
   <structfield>rolcanlogin</structfield>, which is an approximation to the set
   of roles that are being used as groups.
  </para>

  <table>
   <title><structname>pg_group</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>groname</structfield> <type>name</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>rolname</structfield>)
      </para>
      <para>
       Name of the group
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>grosysid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       ID of this group
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>grolist</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       An array containing the IDs of the roles in this group
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="view-pg-hba-file-rules">
  <title><structname>pg_hba_file_rules</structname></title>

  <indexterm zone="view-pg-hba-file-rules">
   <primary>pg_hba_file_rules</primary>
  </indexterm>

  <para>
   The view <structname>pg_hba_file_rules</structname> provides a summary of
   the contents of the client authentication configuration