Add section to Migration talking about typical areas that change between

major releases.

doc/src/sgml/backup.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.113 2008/01/23 20:21:37 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.114 2008/02/13 22:44:06 momjian Exp $ -->
 
 <chapter id="backup">
  <title>Backup and Restore</title>
@@ -1909,13 +1909,6 @@ pg_dumpall -p 5432 | psql -d postgres -p 6543
    of downtime for an upgrade.
   </para>
 
-  <para>
-   In practice you probably want to test your client
-   applications on the new setup before switching over completely.
-   This is another reason for setting up concurrent installations
-   of old and new versions.
-  </para>
-
   <para>
    If you cannot or do not want to run two servers in parallel, you can
    do the backup step before installing the new version, bring down
@@ -1955,5 +1948,68 @@ psql -f backup postgres
     moving an installation like this will not work.)
    </para>
   </note>
+
+  <para>
+   In practice you probably want to test your client applications on the
+   new version before switching over completely.  This is another reason
+   for setting up concurrent installations of old and new versions.  When
+   testing a <productname>PostgreSQL</> major upgrade, consider the
+   following categories of possible changes:
+  </para>
+
+  <variablelist>
+
+   <varlistentry>
+    <term>Administration</term>
+    <listitem>
+     <para>
+      The capabilities available for administrators to monitor and control
+      the server often change and improve in each major release.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term>SQL</term>
+    <listitem>
+     <para>
+      Typically this includes new SQL command capabilities and not changes
+      in behavior, unless specifically mentioned in the release notes.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term>Library API</term>
+    <listitem>
+     <para>
+      Typically libraries like <application>libpq</> only add new
+      functionality, again unless mentioned in the release notes.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term>System Catalogs</term>
+    <listitem>
+     <para>
+      System catalog changes usually only affect database management tools.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term>Server C-language API</term>
+    <listitem>
+     <para>
+      This involved changes in the backend function API, which is written
+      in the C programming language.  Such changes effect code that
+      references backend functions deep inside the server.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
  </sect1>
 </chapter>