declare 
  xsdclob clob := '<?xml version="1.0" encoding="windows-1251"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:simpleType name="mynumber">
    <xs:restriction base="xs:decimal">
      <xs:pattern value="\-{0,1}[0-9]+\.[0-9]{2}"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="mymask">
    <xs:restriction base="xs:string">
      <xs:maxLength value="7"/>
      <xs:minLength value="4"/>
      <xs:pattern value="([0-9]{2})(\.)((([0-9])|([0-9]{2}))|([0-9]{2}))"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:element name="DATA" type="DATACONTENT"/>
  <xs:complexType name="DATACONTENT">
    <xs:sequence>
      <xs:element name="VALUE1" type="mynumber" nillable="true" minOccurs="0"/>
      <xs:element name="VALUE2" type="mymask" nillable="true" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>';
begin
  begin
    dbms_xmlschema.deleteschema('myxsd.xsd', 3); 
  exception
    when others then
      null;
  end;
  begin
    dbms_xmlschema.registerSchema('myxsd.xsd', xsdclob, local => true, genTypes => false, genbean => false, genTables => false);
  exception
    when others then
      null;
  end;
end;

declare 
  xml xmltype;
  xml_clob clob := '<?xml version="1.0" encoding="windows-1251"?>
<DATA>
  <VALUE1>12.34</VALUE1>
  <VALUE2>11.22</VALUE2>
</DATA>';
  xml_clob1 clob := '<?xml version="1.0" encoding="windows-1251"?>
<DATA>
  <VALUE1>2.10</VALUE1>
  <VALUE2>22.5</VALUE2>
</DATA>';
begin
  --execute immediate 'alter session set nls_numeric_characters = ''. ''';
  begin
    xml := xmltype(xml_clob);
    dbms_output.put_line('isschemavalid : ' ||case when xml.isschemavalid('myxsd.xsd') = 1 then 'OK' else 'ERROR' end);  
    xml := xml.createSchemaBasedXML('myxsd.xsd');
    xmltype.schemaValidate(xml);
  EXCEPTION
    when OTHERS then
      dbms_output.put_line('schemaValidate : ERROR ' ||sqlerrm);
  end;
  dbms_output.put_line('');
  begin
    xml := xmltype(xml_clob1);
    dbms_output.put_line('isschemavalid : ' ||case when xml.isschemavalid('myxsd.xsd') = 1 then 'OK' else 'ERROR' end);  
    xml := xml.createSchemaBasedXML('myxsd.xsd');
    xmltype.schemaValidate(xml);
  EXCEPTION
    when OTHERS then
      dbms_output.put_line('schemaValidate : ERROR ' ||sqlerrm);
  end;
end;

isschemavalid : ERROR
schemaValidate : ERROR ORA-31154: недопустимый документ XML
ORA-19202: Возникла ошибка при обработке XML 
LSX-00333: литерал "11.22" не является допустимым в отношении шаблона

isschemavalid : OK
schemaValidate : ERROR ORA-31154: недопустимый документ XML
ORA-19202: Возникла ошибка при обработке XML 
LSX-00333: литерал "2.1" не является допустимым в отношении шаблона