In a memory hierarchy system having two or more hierarchy storages of different access speeds and programs and/or data to be loaded on the hierarchy storages, an activity information acquisition unit and a display unit are provided to present information regarding selection of programs and/or data to be loaded on a higher level in memory hierarchy, a unit is provided which automatically decides loading of the programs and/or data on the higher level and executes reallocation of the programs and/or data on the basis of the information, and a unit is provided which permits the user to change the loading by using a user command. The user can make full use of these units during execution of the memory hierarchy control. In an embodiment, priority for the programs and/or data to be loaded on the higher level is calculated and decided. The programs and/or data are written into the real storage in accordance with their priority to increase the real storage hit rate upon occurrence of a next request for loading.