PURPOSE: To load collectively segments in accordance with the attribution of the segment included in one page at the generation of page absence by specifying whether strong mutual relation of respective information in the segments exists or not.

CONSTITUTION: If page absence is generated at the execution of a program, the processing state is set up in a memory map table entry MME. To transfer information to a main storage page frame newly assigned from a backing store (BKST), a page discriber PD corresponding to a page to be transferred is read out. A BKST address in which the page to be transferred is stored is obtained on the basis of a real address RPA of the page describer PD. A channel program is formed by using said BKST address as a reading BKST address and a previously assigned page frame No. as a writing address. The formed program transfers one page when collective loading specifying bit L=0 or transfers the whole pages for the collective loading of segments when L=1.