How can I save a Sega Dreamcast cdi file to my CD-R if the file is too big?

How can I save a Sega Dreamcast cdi file to my CD-R if the file is too big? is there a way to shrink the file or split it in half, like if it's a one disk game but it takes 800 MB, can I like split it, put 400 mb on one CD and the the other 400 mb on another disk?