IO triggered a warning. E.g. when
          encountering a corrupted buffer with <xref
          linkend="guc-zero-damaged-pages"/> enabled.
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>ERROR</literal> means the I/O failed with an error.
         </para>
        </listitem>
       </itemizedlist>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>target_desc</structfield> <type>text</type>
      </para>
      <para>
       Description of what the I/O operation is targeting.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>f_sync</structfield> <type>bool</type>
      </para>
      <para>
       Flag indicating whether the I/O is executed synchronously.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>f_localmem</structfield> <type>bool</type>
      </para>
      <para>
       Flag indicating whether the I/O references process local memory.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>f_buffered</structfield> <type>bool</type>
      </para>
      <para>
       Flag indicating whether the I/O is buffered I/O.
      </para></entry>
     </row>

    </tbody>
   </tgroup>
  </table>

  <para>
   The <structname>pg_aios</structname> view is read-only.
  </para>

  <para>
   By default, the <structname>pg_aios</structname> view can be read only by
   superusers or roles with privileges of the
   <literal>pg_read_all_stats</literal> role.
  </para>
 </sect1>

 <sect1 id="view-pg-available-extensions">
  <title><structname>pg_available_extensions</structname></title>

  <indexterm zone="view-pg-available-extensions">
   <primary>pg_available_extensions</primary>
  </indexterm>

  <para>
   The <structname>pg_available_extensions</structname> view lists the
   extensions that are available for installation.
   See also the
   <link linkend="catalog-pg-extension"><structname>pg_extension</structname></link>
   catalog, which shows the extensions currently installed.
  </para>

  <table>
   <title><structname>pg_available_extensions</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>name</structfield> <type>name</type>
      </para>
      <para>
       Extension name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>default_version</structfield> <type>text</type>
      </para>
      <para>
       Name of default version, or <literal>NULL</literal> if none is
       specified
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>installed_version</structfield> <type>text</type>
      </para>
      <para>
       Currently installed version of the extension,
       or <literal>NULL</literal> if not installed
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>comment</structfield> <type>text</type>
      </para>
      <para>
       Comment string from the extension's control file
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The <structname>pg_available_extensions</structname> view is read-only.
  </para>
 </sect1>

 <sect1 id="view-pg-available-extension-versions">
  <title><structname>pg_available_extension_versions</structname></title>