doc/src/sgml/ref/checkpoint.sgml

   1 <!-- $PostgreSQL$ -->
   2
   3 <refentry id="sql-checkpoint">
   4  <refmeta>
   5   <refentrytitle id="sql-checkpoint-title">CHECKPOINT</refentrytitle>
   6   <manvolnum>7</manvolnum>
   7   <refmiscinfo>SQL - Language Statements</refmiscinfo>
   8  </refmeta>
   9
  10  <refnamediv>
  11   <refname>CHECKPOINT</refname>
  12   <refpurpose>force a transaction log checkpoint</refpurpose>
  13  </refnamediv>
  14
  15  <indexterm zone="sql-checkpoint">
  16   <primary>CHECKPOINT</primary>
  17  </indexterm>
  18
  19  <refsynopsisdiv>
  20 <synopsis>
  21 CHECKPOINT
  22 </synopsis>
  23  </refsynopsisdiv>
  24
  25  <refsect1>
  26   <title>Description</title>
  27
  28   <para>
  29    Write-Ahead Logging (WAL) puts a checkpoint in the transaction log
  30    every so often. (To adjust the automatic checkpoint interval, see
  31    the run-time configuration options <xref linkend="guc-checkpoint-segments">
  32    and <xref linkend="guc-checkpoint-timeout">.)  The
  33    <command>CHECKPOINT</command> command forces an immediate
  34    checkpoint when the command is issued, without waiting for a
  35    scheduled checkpoint.
  36   </para>
  37
  38   <para>
  39    A checkpoint is a point in the transaction log sequence at which
  40    all data files have been updated to reflect the information in the
  41    log.  All data files will be flushed to disk.  Refer to
  42    <xref linkend="wal"> for more information about the WAL system.
  43   </para>
  44
  45   <para>
  46    Only superusers can call <command>CHECKPOINT</command>.  The command is
  47    not intended for use during normal operation.
  48   </para>
  49  </refsect1>
  50
  51  <refsect1>
  52   <title>Compatibility</title>
  53
  54   <para>
  55    The <command>CHECKPOINT</command> command is a
  56    <productname>PostgreSQL</productname> language extension.
  57   </para>
  58  </refsect1>
  59 </refentry>