You state that you are using Eclipse. However, Eclipse is a development environment for both Linux/Unix and Windows. Which operating system are you using?
Also, an output from RMMAPINX (see RM Users Guide for use) would be helpful in understanding the file's characteristics. Simply looking at size does not tell us much. But RMMAPINX will tell how much space is used for storing the index trees versus the data records, and the amount of compression that is achieved.