role="column_definition">
       <structfield>flush_lsn</structfield> <type>pg_lsn</type>
      </para>
      <para>
       Last write-ahead log location flushed to disk by this standby
       server
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>replay_lsn</structfield> <type>pg_lsn</type>
      </para>
      <para>
       Last write-ahead log location replayed into the database on this
       standby server
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>write_lag</structfield> <type>interval</type>
      </para>
      <para>
       Time elapsed between flushing recent WAL locally and receiving
       notification that this standby server has written it (but not yet
       flushed it or applied it).  This can be used to gauge the delay that
       <literal>synchronous_commit</literal> level
       <literal>remote_write</literal> incurred while committing if this
       server was configured as a synchronous standby.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>flush_lag</structfield> <type>interval</type>
      </para>
      <para>
       Time elapsed between flushing recent WAL locally and receiving
       notification that this standby server has written and flushed it
       (but not yet applied it).  This can be used to gauge the delay that
       <literal>synchronous_commit</literal> level
       <literal>on</literal> incurred while committing if this
       server was configured as a synchronous standby.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>replay_lag</structfield> <type>interval</type>
      </para>
      <para>
       Time elapsed between flushing recent WAL locally and receiving
       notification that this standby server has written, flushed and
       applied it.  This can be used to gauge the delay that
       <literal>synchronous_commit</literal> level
       <literal>remote_apply</literal> incurred while committing if this
       server was configured as a synchronous standby.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>sync_priority</structfield> <type>integer</type>
      </para>
      <para>
       Priority of this standby server for being chosen as the
       synchronous standby in a priority-based synchronous replication.
       This has no effect in a quorum-based synchronous replication.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>sync_state</structfield> <type>text</type>
      </para>
      <para>
       Synchronous state of this standby server.
       Possible values are:
       <itemizedlist>
        <listitem>
         <para>
          <literal>async</literal>: This standby server is asynchronous.
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>potential</literal>: This standby server is now asynchronous,
          but can potentially become synchronous if one of current
          synchronous ones fails.
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>sync</literal>: This standby server is synchronous.
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>quorum</literal>: This standby server is considered as a candidate
          for quorum standbys.
         </para>
        </listitem>
       </itemizedlist>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reply_time</structfield> <type>timestamp with time zone</type>
      </para>