xml file

I create and save an xml in C++

MSXML::IXMLDOMDocumentPtr L_comXmlDoc(__uuidof(MSXML::DOMDocument));

I use createElement to create elements
then I use the save function

My problem is that all my elements
are in memory so I have memory problems
if I have to many elements. Elements
are saved in file only at the end of my code


I would like to create elements
and save them each time in the xml file
to avoid memory problems

Any idea how to do that?