From 5d52ad9dc884ac786cc15b588302d8b0b62451bd Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Mon, 2 Oct 2006 22:33:02 +0000
Subject: [PATCH] Update recovery documentation.
Simon Riggs
---
doc/src/sgml/backup.sgml | 52 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 51 insertions(+), 1 deletion(-)
diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index cff61ad6576..550336575d1 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.88 2006/09/19 19:04:51 neilc Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.89 2006/10/02 22:33:02 momjian Exp $ -->
<chapter id="backup">
<title>Backup and Restore</title>
@@ -1167,6 +1167,48 @@ restore_command = 'copy /mnt/server/archivedir/%f "%p"' # Windows
</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>
@@ -1317,6 +1359,14 @@ restore_command = 'copy /mnt/server/archivedir/%f "%p"' # Windows
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.
--
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