PURPOSE: To prevent the assignment of page frames from being collected on the same main storage device unit and to improve the parallel processing of main storage devices by providing a page frame control means and two temporary storage means.

CONSTITUTION: When a process requests the assignment of a page frame in a main storage device controlling method using a data processing system having plural processors and main storage devices, the contents of a register 9 are stored in a storage part corresponding to a page frame finally assigned out of at least one page frame assigned on the basis of a register 12 and a pointer 10. The contents stored in the storage part corresponding to the finally assigned page frame are stored in the final storage parts of a register 9 and a page frame control table 8. Consequently, the assignment of page frames can be prevented from being collected on the same main storage device unit.