I can't see any reason the reporting engine would hold on to any of the report objects once the Report instance is out of scope. It might cache some things as long as the Report object is still around, just in case you decided to publish the report more than once or maybe edit it. Is your application hanging on to the report? 

Hi Mike,

I think the problem is that the already created files are still kept in memory. So I should clear the memory after the report is created. But I don't know how?

Is there something I have to do after the publishing of the report?

The reporting engine builds the report in-memory before it gets published. So there will always be limits on the size of the report based on the currently-available memory on the machine. Images tend to eat up a lot of memory, so you might want to consider removing them to see if that helps. If your document is very large, you might consider filtering or breaking it down into small pieces, since a single document that is thousands of pages long won't be very useful to most human users, anyway.

Another alternative would be to use the Infragistics.Documents.Word.WordDocumentWriter class to write out a document in Word format. The advantage of the WordDocumentWriter is that it writes the document directly to a file in a linear process - so it doesn't have to keep the entire document in memory and can therefore create much larger documents.