Database Software

Hi, I am using Oracle 9i.

Presently I use following code to create index.

begin
Ctx_Ddl.Drop_Preference ('text_only');
end;
/
begin
Ctx_Ddl.Create_Preference ( 'text_only', 'basic_lexer');
Ctx_Ddl.Set_Attribute ( 'text_only', 'index_text', 'true' );
Ctx_Ddl.Set_Attribute ( 'text_only', 'index_themes', 'false' );
end;
/

CREATE TABLE MY_XML_DOCS(
XML_RES_ID NUMBER (16) NOT NULL,
XML_RES BLOB NOT NULL,
XML_RES_PATH VARCHAR2 (128),
XML_DOCS_CREATED_BY VARCHAR2 (16) NOT NULL,
XML_DOCS_CREATED_DT DATE NOT NULL,
XML_DOCS_MODIFIED_BY VARCHAR2 (16),
XML_DOCS_MODIFIED_DT DATE ) ;

drop index FULL_TEXT_INDEX ;
create INDEX FULL_TEXT_INDEX ON MY_XML_DOCS(XML_RES)
INDEXTYPE IS ctxsys.CONTEXT
parameters ('lexer text_only stoplist ctxsys.empty_stoplist');

BEGIN
CTX_DDL.sync_index('FULL_TEXT_INDEX ','10M');
END;

And I've some XML documents stored in blob columns in the above table. But my query with 'contains' param does not return expected results.(it presently returns no results). Do I miss anything? Do I need to specify any thing else while I create the Index? Kindly advice.