<entry><link linkend="view-pg-shadow"><structname>pg_shadow</structname></link></entry>
      <entry>database users</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-shmem-allocations"><structname>pg_shmem_allocations</structname></link></entry>
      <entry>shared memory allocations</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-shmem-allocations-numa"><structname>pg_shmem_allocations_numa</structname></link></entry>
      <entry>NUMA node mappings for shared memory allocations</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-stats"><structname>pg_stats</structname></link></entry>
      <entry>planner statistics</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-stats-ext"><structname>pg_stats_ext</structname></link></entry>
      <entry>extended planner statistics</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-stats-ext-exprs"><structname>pg_stats_ext_exprs</structname></link></entry>
      <entry>extended planner statistics for expressions</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-tables"><structname>pg_tables</structname></link></entry>
      <entry>tables</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link></entry>
      <entry>time zone abbreviations</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-timezone-names"><structname>pg_timezone_names</structname></link></entry>
      <entry>time zone names</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-user"><structname>pg_user</structname></link></entry>
      <entry>database users</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-user-mappings"><structname>pg_user_mappings</structname></link></entry>
      <entry>user mappings</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-views"><structname>pg_views</structname></link></entry>
      <entry>views</entry>
     </row>

     <row>
      <entry><link linkend="view-pg-wait-events"><structname>pg_wait_events</structname></link></entry>
      <entry>wait events</entry>
     </row>

    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="view-pg-aios">
  <title><structname>pg_aios</structname></title>

  <indexterm zone="view-pg-aios">
   <primary>pg_aios</primary>
  </indexterm>

  <para>
   The <structname>pg_aios</structname> view lists all <xref
   linkend="glossary-aio"/> handles that are currently in-use.  An I/O handle
   is used to reference an I/O operation that is being prepared, executed or
   is in the process of completing.  <structname>pg_aios</structname> contains
   one row for each I/O handle.
  </para>

  <para>
   This view is mainly useful for developers of
   <productname>PostgreSQL</productname>, but may also be useful when tuning
   <productname>PostgreSQL</productname>.
  </para>

  <table>
   <title><structname>pg_aios</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>pid</structfield> <type>int4</type>
      </para>
      <para>
       Process ID of the server process that is issuing this I/O.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>io_id</structfield> <type>int4</type>
      </para>
      <para>
       Identifier of the I/O handle. Handles are reused once the I/O
       completed (or if the handle is released before I/O is started). On reuse
       <link linkend="view-pg-aios-io-generation">
        <structname>pg_aios</structname>.<structfield>io_generation</structfield>
       </link>
       is incremented.