A TLB provided in a memory management apparatus stores an entry for each
logical page, and each entry holds an address of a physical page mapped
to a corresponding logical page, an index showing the degradation degree
of the physical page, and an index showing the access frequency to the
logical page. The memory management apparatus accesses a physical page
mapped to a desired logical page according to the data stored in the TLB,
periodically exchanges the contents between a first physical page mapped
to a specific logical page having a largest access frequency index and a
second physical page having a smallest degradation index, and then maps
the specific logical page to the second physical page. Through the
physical page exchange and corresponding mapping process, accesses to
each physical page are distributed, so that degradation in storage
function is substantially equalized.