Use projects archiving to reduce the amount of managed projects, thus the current file size, by removing the unnecessary ones (e.g.: closed projects) and saving them in sepparate files. When needed they can be restored and inserted back in the working file.

Go to Project Portfolio View.

From Project menu, Archive project... , the current project will be saved as a RationalPlan Single Project (.xrp) file.

From Project menu, Restore project... , a previously archived project will be inserted back in the Project Portfolio.