an access control apparatus , method , and recording medium for storing a program , provides equal input / output opportunities to auxiliary memory units for all users by attaching priority information for each user to user - entered io commands . the prioritized io commands are stored in an io queue corresponding to a particular one of the auxiliary memory units , and physical io is performed on each of the auxiliary memory units in the sequence of priority information attached to the prioritized io commands in each io queue irrespective of who the entrant users are .