procedure TForm1.Button1Click(Sender: TObject);
//insert into my_xml values(3, :PFX,  XMLType(:XML, nls_charset_id('CL8MSWIN1251')))
// Структура my_xml
//|Поле      |Тип       |Длина  |Точность  |Null        |Default  |Комментарии  
//|SID       |NUMBER    |22     |          |Not null !  |         |             
//|FILE_XML  |VARCHAR2  |15     |          |Y           |         |             
//|XT        |XMLTYPE   |2000   |          |Y           |         |             

var LOB: TLOBLocator;
  Buffer: array[0..4095] of char;
  f: file;
  numRead: Integer;
begin
  if not OpenDialog.Execute then Exit;
  if not os.Connected then os.Connected := True;

  with oq do
  begin

    LOB := TLOBLocator.CreateTemporary(os, otBLOB, True);
    AssignFile(f, OpenDialog.FileName);
    Reset(f, 1);
    repeat
      BlockRead(f, Buffer, SizeOf(Buffer), numRead);
      LOB.Write(Buffer, numRead);
    until (NumRead = 0) or (SizeOf(Buffer) <> NumRead);
    CloseFile(f);

    SetComplexVariable('XML', LOB);
    SetVariable('PFX', ExtractFileName(OpenDialog.FileName));
    Execute;
    LOB.Free;

  end;

  os.Connected := False;

end;