SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
                                ^^^^ required

Also note that SET TRANSACTION ISOLATION LEVEL change
isolevel for _current_ transaction, in accordance with
standard, not for session (ALTER SESSION is used in Oracle,
but it's not implemented currently).

And I would don't mention SET XACTISOLEVEL TO ...
form at all.

Please update set.sgml - I failed to understand all these

SET TIME ZONE { '<REPLACEABLE CLASS="PARAMETER">

now.


for Vadim

doc/src/sgml/ref/set.sgml

@@ -534,7 +534,7 @@ SET TIME ZONE { '<REPLACEABLE CLASS="PARAMETER">timezone</REPLACEABLE>' | LOCAL
       </term>
       <listitem>
        <para>
-	Sets the isolation level for transactions.
+	Sets the isolation level for the current transaction.
 	
 	<variablelist>
 	 <varlistentry>
@@ -543,7 +543,7 @@ SET TIME ZONE { '<REPLACEABLE CLASS="PARAMETER">timezone</REPLACEABLE>' | LOCAL
 	  </term>
 	  <listitem>
 	   <para>
-		Sets the isolation level for transactions to
+		Sets the isolation level for the current transaction to
 		'SERIALIZABLE' or 'READ COMMITTED'.
 	   </para>
 	  </listitem>
@@ -556,7 +556,7 @@ SET TIME ZONE { '<REPLACEABLE CLASS="PARAMETER">timezone</REPLACEABLE>' | LOCAL
 	  </term>
 	  <listitem>
 	   <para>
-		Sets the isolation level for transactions to
+		Sets the isolation level for the current transaction to
 		'SERIALIZABLE' or 'COMMITTED'.
 	   </para>
 	  </listitem>

src/man/set.l

 .\" This is -*-nroff-*-
 .\" XXX standard disclaimer belongs here....
-.\" $Header: /cvsroot/pgsql/src/man/Attic/set.l,v 1.19 1999/06/03 20:42:18 momjian Exp $
+.\" $Header: /cvsroot/pgsql/src/man/Attic/set.l,v 1.20 1999/06/03 20:44:28 momjian Exp $
 .TH SET SQL 05/14/97 PostgreSQL PostgreSQL
 .SH NAME
 set - set run-time parameters for session
@@ -82,7 +82,7 @@ The default is unlimited.
 sets your timezone.
 .PP
 .I TRANSACTION ISOLATION LEVEL
-sets the transaction isolation level to
+sets the current transaction's isolation level to
 .IR SERIALIZABLE
 or
 .IR READ COMMITTED .