Is the full text of an IOdictionary stored in RAM for the life of the object?
 

I was mucking around in source files recently and I got the impression that IOdictionaries may be read into RAM once, at creation (assuming that the source dictionary file isn't changed during execution), and that all subsequent lookup operations are performed by parsing data from RAM, rather than disk. I didn't dig deep enough to be sure - can anyone confirm or deny this? I'm particularly curious whether this means that the full text of the dictionary is stored in RAM for the life of the object.

I'm concerned because I'm using a custom dictionary to store tabulated model data. The data file is about 300 MB in ASCII format - if this text is being held in RAM for the duration of my program, even after it's been parsed and the data has been read into a program-usable format, then this is a big waste.