Index: doc/src/sgml/backup.sgml
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RCS file: /projects/cvsroot/pgsql/doc/src/sgml/backup.sgml,v
retrieving revision 2.86
diff -c -r2.86 backup.sgml
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--- doc/src/sgml/backup.sgml	20 Sep 2006 12:43:55 -0000
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     </para>
    </sect2>
  
+   <sect2 id="backup-incremental-updated">
+    <title>Incrementally Updated Backups</title>
+ 
+   <indexterm zone="backup">
+    <primary>incrementally updated backups</primary>
+   </indexterm>
+ 
+   <indexterm zone="backup">
+    <primary>change accumulation</primary>
+   </indexterm>
+ 
+    <para>
+     Restartable Recovery can also be utilised to offload the expense of
+     taking periodic base backups from a main server, by instead backing
+     up a Standby server's files.  This concept is also generally known as 
+     incrementally updated backups, log change accumulation or more simply,
+     change accumulation.
+    </para>
+ 
+    <para>
+     If we take a backup of the server files whilst a recovery is in progress,
+     we will be able to restart the recovery from the last restartpoint. 
+     That backup now has many of the changes from previous WAL archive files,
+     so this version is now an updated version of the original base backup.
+     If we need to recover, it will be faster to recover from the 
+     incrementally updated backup than from the base backup.
+    </para>
+ 
+    <para>
+     To make use of this capability you will need to set up a Standby database
+     on a second system, as described in <xref linkend="warm-standby">. By
+     taking a backup of the Standby server while it is running you will
+     have produced an incrementally updated backup. Once this configuration
+     has been implemented you will no longer need to produce regular base 
+     backups of the Primary server: all base backups can be performed on the 
+     Standby server. If you wish to do this, it is not a requirement that you
+     also implement the failover features of a Warm Standby configuration,
+     though you may find it desirable to do both.
+    </para>
+ 
+   </sect2>
+ 
    <sect2 id="continuous-archiving-caveats">
     <title>Caveats</title>
  
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     really offers a solution for Disaster Recovery, not HA.
    </para>
  
+    <para>
+     When running a Standby Server, backups can be performed on the Standby
+     rather than the Primary, thereby offloading the expense of
+     taking periodic base backups. (See 
+     <xref linkend="backup-incremental-updated">)
+    </para>
+ 
+ 
    <para>
     Other mechanisms for High Availability replication are available, both
     commercially and as open-source software.