TXMLObjectAccessor.xquery(TQuery query, int quantity)

The javadoc says :

As the commit invalidates the TXMLObjectIterator which i need to display the results of my query, i would like to know where to call it (after the loop where i iterate on my TResponse with the iterator ?) to do things in a clean way and if i really need to call it (i have tried without and i get my result…).

thks in advance for your answers