A data management method is adapted to a hierarchical virtual storage system which virtually uses a library apparatus having a plurality of recording media as a portion of a hard disk apparatus. The data management method manages loading of the recording media to the library apparatus and unloading of the recording media from the library apparatus in a database in units of a set that is formed by a plurality of recording media, and forms a logical volume, which is a recording unit of a data file with respect to the library apparatus, by one or a plurality of recording media, and manages the logical volume in the database in correspondence with the set.