<!--
doc/src/sgml/ref/pg_waldump.sgml
PostgreSQL documentation
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<refentry id="pgwaldump">
 <indexterm zone="pgwaldump">
  <primary>pg_waldump</primary>
 </indexterm>

 <refmeta>
  <refentrytitle><application>pg_waldump</application></refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo>Application</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>pg_waldump</refname>
  <refpurpose>display a human-readable rendering of the write-ahead log of a <productname>PostgreSQL</productname> database cluster</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>pg_waldump</command>
   <arg rep="repeat" choice="opt"><option>option</option></arg>
   <arg choice="opt"><option>startseg</option><arg choice="opt"><option>endseg</option></arg></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1 id="r1-app-pgwaldump-1">
  <title>Description</title>
  <para>
   <command>pg_waldump</command> displays the write-ahead log (WAL) and is mainly
   useful for debugging or educational purposes.
  </para>

  <para>
   This utility can only be run by the user who installed the server, because
   it requires read-only access to the data directory.
  </para>
 </refsect1>

 <refsect1>
  <title>Options</title>

   <para>
    The following command-line options control the location and format of the
    output:

    <variablelist>

     <varlistentry>
      <term><replaceable class="parameter">startseg</replaceable></term>
      <listitem>
       <para>
        Start reading at the specified WAL segment file.  This implicitly determines
        the path in which files will be searched for, and the timeline to use.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="parameter">endseg</replaceable></term>
      <listitem>
       <para>
        Stop after reading the specified WAL segment file.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-b</option></term>
      <term><option>--bkp-details</option></term>
      <listitem>
       <para>
        Output detailed information about backup blocks.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-B <replaceable>block</replaceable></option></term>
      <term><option>--block=<replaceable>block</replaceable></option></term>
      <listitem>
       <para>
        Only display records that modify the given block.  The relation must
        also be provided with <option>--relation</option> or
        <option>-R</option>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-e <replaceable>end</replaceable></option></term>
      <term><option>--end=<replaceable>end</replaceable></option></term>
      <listitem>
       <para>
        Stop reading at the specified WAL location, instead of reading to the
        end of the log stream.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-f</option></term>
      <term><option>--follow</option></term>
      <listitem>
       <para>
        After reaching the end of valid WAL, keep polling once per second for
        new WAL to appear.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-F <replaceable>fork</replaceable></option></term>
      <term><option>--fork=<replaceable>fork</replaceable></option></term>
      <listitem>
       <para>
        Only display records that modify blocks in the given fork.
        The valid values are <literal>main</literal> for the main fork,
        <literal>fsm</literal> for the free space map,
        <literal>vm</literal> for the visibility map,
        and <literal>init</literal> for the init fork.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-n <replaceable>limit</replaceable></option></term>
      <term><option>--limit=<replaceable>limit</replaceable></option></term>
      <listitem>