Update PITR wording, per Simon.

doc/src/sgml/backup.sgml

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-$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.64 2005/04/18 17:40:40 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.65 2005/04/19 01:39:50 momjian Exp $
 -->
 <chapter id="backup">
  <title>Backup and Restore</title>
@@ -742,12 +742,14 @@ SELECT pg_stop_backup();
     number in the file name stands for an exact position within the WAL
     file, and can ordinarily be ignored.) Once you have safely archived
     the file system backup and the WAL segment files used during the
-    backup (as specified in the backup history file), you can delete all 
-    archived WAL segments with names numerically less. Keep in mind that 
-    only completed WAL segment files are archived, so there will be delay
-    between running <function>pg_stop_backup</> and the archiving of
-    all WAL segment files needed to make the file system backup
-    consistent.
+    backup (as specified in the backup history file), all archived WAL
+    segments with names numerically less are no longer needed to recover
+    the file system backup and may be deleted. However, you should
+    consider keeping several backup sets to be absolutely certain that
+    you are can recover your data. Keep in mind that only completed WAL
+    segment files are archived, so there will be delay between running
+    <function>pg_stop_backup</> and the archiving of all WAL segment
+    files needed to make the file system backup consistent.
    </para>
    <para>
     The backup history file is just a small text file. It contains the