Unpredictable problem using XMLTYPE in Oracle 11g?

Question

We recently upgraded from Oracle 10g to Oracle 11g, which caused some of our stored procedures to start acting funny.
Our database stores BLOBs containing XML data in a table. We then asynchronously convert these BLOBs into XMLTYPE objects, and use them to perform operations in our database. This logic started failing when we moved to 11g.
Our original code looked like this:
PROCEDURE submitTpfdd(shipmentDataId IN VARCHAR2) AS
     shipmentData XMLTYPE;
  csid INTEGER;
  shipmentName VARCHAR(128);
  gk_namespaces VARCHAR(1024) := 'xmlns:a="http://my.app/1.0.0.0"';
BEGIN
  SELECT NLS_CHARSET_ID('UTF8') INTO csid FROM dual;
  SELECT XMLTYPE(tf.shipmentData, csid)
    INTO shipmentData
    FROM SHIPQ.SHIPMENT_FILE tf
    WHERE tf.shipment_id = shipmentDataId;
  shipmentName := shipmentData.extract('/a:Shipment/shipmentName/text()', gk_namespaces).getStringVal();
  ... (more logic)
END submitTpfdd;When we switched to 11g, this code started frequently failing with an "unsupported character set" error. It happens about half the time, and it's unpredictable. It will sometimes pass and sometimes fail, even if the same BLOB is being read both times. I haven't been able to reproduce the error with any of XMLTYPE's other constructors.
Has anybody encountered similar behavior with the XMLTYPE in 11g? Should I submit a tracker?

Answer 1

I have created a SQL program which can be run independently to reproduce the problem.
DECLARE namespaces constant VARCHAR2(1024) := 'xmlns:a="http://morton.com/"';
CURSOR cursor0(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor1(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor2(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor3(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor4(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor5(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor6(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor7(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor8(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
CURSOR cursor9(reeves XMLTYPE) IS
SELECT EXTRACT(VALUE(t), 'text()').getstringval() AS
bullock
FROM TABLE(xmlsequence(reeves.EXTRACT('/a:hopper', namespaces))) t;
xml_clob CLOB := empty_clob;
xml_blob BLOB := empty_blob;
xml_varchar VARCHAR2(4000);
xml_xmltype XMLTYPE;
warning INTEGER;
dest_offset INTEGER := 1;
src_offset INTEGER := 1;
lang_context INTEGER := 0;
char_set INTEGER := nls_charset_id('UTF8');
BEGIN
  dbms_lob.createtemporary(xml_clob, TRUE);
  dbms_lob.createtemporary(xml_blob, TRUE);
  dbms_lob.OPEN(xml_clob, dbms_lob.lob_readwrite);
  dbms_lob.OPEN(xml_blob, dbms_lob.lob_readwrite);
  xml_varchar := '<a:hopper xmlns:a="http://morton.com"/>';
  dbms_lob.writeappend(xml_clob, length(xml_varchar), xml_varchar);
  dbms_lob.converttoblob(xml_blob, xml_clob, dbms_lob.lobmaxsize, dest_offset, src_offset, char_set, lang_context, warning);
  xml_xmltype := XMLTYPE(xml_blob, char_set);
  FOR daniels IN cursor0(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor1(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor2(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor3(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor4(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor5(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor6(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor7(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor8(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
  FOR daniels IN cursor9(xml_xmltype)
  LOOP
    CONTINUE;
  END LOOP;
END;If someone else could run this program and verify that it acts unpredictably, that would be helpful. I have submitted a metalink tracker but the person who is working the tracker is not able to duplicate the same behavior.