diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
new file mode 100644
index d4a1d36..c5851af
*** a/doc/src/sgml/catalogs.sgml
--- b/doc/src/sgml/catalogs.sgml
***************
*** 6930,6936 ****
        <entry>
         OID of the database in which the object exists, or
         zero if the object is a shared object, or
!        null if the object is a transaction ID
        </entry>
       </row>
       <row>
--- 6930,6936 ----
        <entry>
         OID of the database in which the object exists, or
         zero if the object is a shared object, or
!        null if the lock object is on a transaction ID
        </entry>
       </row>
       <row>
***************
*** 6938,6945 ****
        <entry><type>oid</type></entry>
        <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
        <entry>
!        OID of the relation, or null if the object is not
!        a relation or part of a relation
        </entry>
       </row>
       <row>
--- 6938,6945 ----
        <entry><type>oid</type></entry>
        <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
        <entry>
!        OID of the relation, or null if the lock object is not
!        on a relation or part of a relation
        </entry>
       </row>
       <row>
***************
*** 6947,6954 ****
        <entry><type>integer</type></entry>
        <entry></entry>
        <entry>
!        Page number within the relation, or null if the object
!        is not a tuple or relation page
        </entry>
       </row>
       <row>
--- 6947,6954 ----
        <entry><type>integer</type></entry>
        <entry></entry>
        <entry>
!        Page number within the relation, or null if the lock object
!        is not on a tuple or relation page
        </entry>
       </row>
       <row>
***************
*** 6956,6962 ****
        <entry><type>smallint</type></entry>
        <entry></entry>
        <entry>
!        Tuple number within the page, or null if the object is not a tuple
        </entry>
       </row>
       <row>
--- 6956,6963 ----
        <entry><type>smallint</type></entry>
        <entry></entry>
        <entry>
!        Tuple number within the page, or null if the lock object is not
!        on a tuple
        </entry>
       </row>
       <row>
***************
*** 6964,6971 ****
        <entry><type>text</type></entry>
        <entry></entry>
        <entry>
!        Virtual ID of a transaction, or null if the object is not a
!        virtual transaction ID
        </entry>
       </row>
       <row>
--- 6965,6972 ----
        <entry><type>text</type></entry>
        <entry></entry>
        <entry>
!        Virtual ID of a transaction lock, or null if the lock object is not
!        on a virtual transaction ID
        </entry>
       </row>
       <row>
***************
*** 6973,6979 ****
        <entry><type>xid</type></entry>
        <entry></entry>
        <entry>
!        ID of a transaction, or null if the object is not a transaction ID
        </entry>
       </row>
       <row>
--- 6974,6980 ----
        <entry><type>xid</type></entry>
        <entry></entry>
        <entry>
!        ID of a transaction lock, or null if the lock object is not on a transaction ID
        </entry>
       </row>
       <row>
***************
*** 6982,6988 ****
        <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
        <entry>
         OID of the system catalog containing the object, or null if the
!        object is not a general database object
        </entry>
       </row>
       <row>
--- 6983,6989 ----
        <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
        <entry>
         OID of the system catalog containing the object, or null if the
!        lock object is not on a general database object.
        </entry>
       </row>
       <row>
***************
*** 6991,6997 ****
        <entry>any OID column</entry>
        <entry>
         OID of the object within its system catalog, or null if the
!        object is not a general database object.
         For advisory locks it is used to distinguish the two key
         spaces (1 for an int8 key, 2 for two int4 keys).
        </entry>
--- 6992,6998 ----
        <entry>any OID column</entry>
        <entry>
         OID of the object within its system catalog, or null if the
!        lock object is not on a general database object.
         For advisory locks it is used to distinguish the two key
         spaces (1 for an int8 key, 2 for two int4 keys).
        </entry>
***************
*** 7004,7010 ****
         For a table column, this is the column number (the
         <structfield>classid</> and <structfield>objid</> refer to the
         table itself).  For all other object types, this column is
!        zero.  Null if the object is not a general database object
        </entry>
       </row>
       <row>
--- 7005,7011 ----
         For a table column, this is the column number (the
         <structfield>classid</> and <structfield>objid</> refer to the
         table itself).  For all other object types, this column is
!        zero.  Null if the lock object is not on a general database object.
        </entry>
       </row>
       <row>