procedure test_reg
is
 l_xsd_test varchar2(4000) :=    
  '<xsd:schema targetNamespace="urn:TEST" 
  xmlns="urn:TEST" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  xmlns:xdb="http://xmlns.oracle.com/xdb">      
          <xsd:element name="issueDate" type="xsd:dateTime" xdb:SQLType="TIMESTAMP WITH TIME ZONE" form="qualified"/>[
   </xsd:schema>';
BEGIN

DBMS_XMLSCHEMA.registerSchema (
     SCHEMAURL => 'http://test.com/xsd/TEST.xsd'
    ,SCHEMADOC => l_xsd_test
  );
END;

procedure test_validate
is
  l_xml xmltype;                                                                  
  l_txt clob := '<?xml version="1.0" encoding="UTF-8"?>   
   <ns0:issueDate xmlns:ns0="urn:TEST">2018-02-06T12:07:25.141+03:00</ns0:issueDate>';
begin

  l_xml := xmltype(xmlData => l_txt, schema => 'http://test.com/xsd/TEST.xsd');

  l_xml.schemavalidate();
exception
when OTHERS then
  log(sqlerrm);
end;

 type="xsd:dateTime" xdb:SQLType="TIMESTAMP WITH TIME ZONE" 

TIME ZONE" form="qualified"/> [

ALTER SESSION SET nls_numeric_characters = '.,'