Size of oninit process on WinNT

Can someone please explain why the amount of memory allocated to the oninit.exe process only seems to increase over time? I would think that even after closing all connections to the database, at least some of the memory allocated to the process should be freed. However, this is not the case. Informix tech support said to run onmode -F (?!?!!) to release a virtual memory segment that had been added. The size of oninit.exe process actually grew. What is going on? Thanks. Jeff