Oracle 11g Release 2

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
create table t_table (xml_conf) as
select to_clob('<ns2:ConfigurationTree xmlns:ns2="com.cameleon.business.xml.configurationTree-7.1.0.0" xmlns="com.cameleon.business.xml.settingsTree-7.1.0.0">
<ns2:ConfigurableProduct>
    <ns2:CPNode name="cpX">
        <ns2:FormProperty name="fpX">
            <ns2:SingleValuation isCommentUserChoice="false" isValueUserChoice="false" isQtyUserChoice="false">
                <ns2:Value>
                    <ns2:textValue/>
                </ns2:Value>
            </ns2:SingleValuation>
        </ns2:FormProperty>
    </ns2:CPNode>
</ns2:ConfigurableProduct>
</ns2:ConfigurationTree>') from dual
union all
select to_clob('<ns2:ConfigurationTree xmlns:ns2="com.cameleon.business.xml.configurationTree-7.1.0.0" xmlns="com.cameleon.business.xml.settingsTree-7.1.0.0">
<ns2:ConfigurableProduct>
    <ns2:CPNode name="cpX">
        <ns2:FormProperty name="fpX">
            <ns2:SingleValuation isCommentUserChoice="false" isValueUserChoice="false" isQtyUserChoice="false">
                <ns2:Value>
                    <ns2:textValue>123456</ns2:textValue>
                </ns2:Value>
            </ns2:SingleValuation>
        </ns2:FormProperty>
    </ns2:CPNode>
</ns2:ConfigurableProduct>
</ns2:ConfigurationTree>') from dual;
2 rows affected

update T_TABLE set XML_CONF = updatexml(xmltype(XML_CONF),
  '//FormProperty[@name="fpX"]//Value/textValue/text()','78910',
  '//FormProperty[@name="fpX"]//Value/textValue[not(text())]',
     xmlelement("ns2:textValue", xmlattributes('com.cameleon.business.xml.settingsTree-7.1.0.0' as "xmlns:ns2"), '78910'),
  'xmlns:ns2="com.cameleon.business.xml.settingsTree-7.1.0.0" xmlns="com.cameleon.business.xml.configurationTree-7.1.0.0"').getClobVal();
2 rows affected

select * from t_table;


XML_CONF


<ns2:ConfigurationTree xmlns:ns2="com.cameleon.business.xml.configurationTree-7.1.0.0" xmlns="com.cameleon.business.xml.settingsTree-7.1.0.0"><ns2:ConfigurableProduct><ns2:CPNode name="cpX"><ns2:FormProperty name="fpX"><ns2:SingleValuation isCommentUserChoice="false" isValueUserChoice="false" isQtyUserChoice="false"><ns2:Value><ns2:textValue xmlns:ns2="com.cameleon.business.xml.settingsTree-7.1.0.0">78910</ns2:textValue></ns2:Value></ns2:SingleValuation></ns2:FormProperty></ns2:CPNode></ns2:ConfigurableProduct></ns2:ConfigurationTree>

<ns2:ConfigurationTree xmlns:ns2="com.cameleon.business.xml.configurationTree-7.1.0.0" xmlns="com.cameleon.business.xml.settingsTree-7.1.0.0"><ns2:ConfigurableProduct><ns2:CPNode name="cpX"><ns2:FormProperty name="fpX"><ns2:SingleValuation isCommentUserChoice="false" isValueUserChoice="false" isQtyUserChoice="false"><ns2:Value><ns2:textValue>78910</ns2:textValue></ns2:Value></ns2:SingleValuation></ns2:FormProperty></ns2:CPNode></ns2:ConfigurableProduct></ns2:ConfigurationTree>


select xmlserialize(document xmltype(xml_conf) indent) from t_table;


XMLSERIALIZE(DOCUMENTXMLTYPE(XML_CONF)INDENT)


<ns2:ConfigurationTree xmlns:ns2="com.cameleon.business.xml.configurationTree-7.1.0.0" xmlns="com.cameleon.business.xml.settingsTree-7.1.0.0">
  <ns2:ConfigurableProduct>
    <ns2:CPNode name="cpX">
      <ns2:FormProperty name="fpX">
        <ns2:SingleValuation isCommentUserChoice="false" isValueUserChoice="false" isQtyUserChoice="false">
          <ns2:Value>
            <ns2:textValue xmlns:ns2="com.cameleon.business.xml.settingsTree-7.1.0.0">78910</ns2:textValue>
          </ns2:Value>
        </ns2:SingleValuation>
      </ns2:FormProperty>
    </ns2:CPNode>
  </ns2:ConfigurableProduct>
</ns2:ConfigurationTree>


<ns2:ConfigurationTree xmlns:ns2="com.cameleon.business.xml.configurationTree-7.1.0.0" xmlns="com.cameleon.business.xml.settingsTree-7.1.0.0">
  <ns2:ConfigurableProduct>
    <ns2:CPNode name="cpX">
      <ns2:FormProperty name="fpX">
        <ns2:SingleValuation isCommentUserChoice="false" isValueUserChoice="false" isQtyUserChoice="false">
          <ns2:Value>
            <ns2:textValue>78910</ns2:textValue>
          </ns2:Value>
        </ns2:SingleValuation>
      </ns2:FormProperty>
    </ns2:CPNode>
  </ns2:ConfigurableProduct>
</ns2:ConfigurationTree>