Server-side script calls EndIterator when it stops iterating over the object's items. The object uses this method to perform any clean-up to reflect the fact that it is no longer iterating over its items. 

OwnerData is a pointer to information that the object can use to influence the iteration process. Each object stores and uses this information in its own way. This information is first supplied by the initial call to the StartIterator method. It is passed to each NextIteration call (which can modify the information), and finally supplied to the EndIterator method, which can free the memory used to store the information. 

StartIterator 

NextIteration