This one is similar in concept to the usage of the word ramdrive in the IBM PC world. It concerns configuring a portion of memory to behave like disk which speeds up programs that are I/O intensive particularly when disks are relatively slow. The catch is that there must be enough memory available to contain the disk data. In MOM, this option defines a huge memory array and replaces all reads and writes to disk with copying variables into or out of locations in this huge array. This is done at the lowest subroutine levels so that the higher level routines look the same regardless of whether this I/O option is used or not. This option is not specific to any computer platform and therefore makes MOM highly portable.