Point out that TRUNCATE can't be used inside a transaction block.

doc/src/sgml/ref/truncate.sgml

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-$Header: /cvsroot/pgsql/doc/src/sgml/ref/truncate.sgml,v 1.3 2001/09/03 12:57:50 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/truncate.sgml,v 1.4 2001/11/18 21:14:20 tgl Exp $
 Postgres documentation
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@@ -84,7 +84,13 @@ TRUNCATE
    <command>TRUNCATE</command> quickly removes all rows from a
    table. It has the same effect as an unqualified
    <command>DELETE</command> but since it does not actually scan the
-   table it is faster. This is most effective on large tables.
+   table it is faster. This is most useful on large tables.
+  </para>
+
+  <para>
+   <command>TRUNCATE</command> cannot be executed inside a transaction
+   block (<command>BEGIN</>/<command>COMMIT</> pair), because there is
+   no way to roll it back.
   </para>
  </refsect1>