Abstract: A virtual magnetic tape drive library system that includes a host computer controller, a tape drive subsystem and a virtual multi-tape cartridge unit is set forth. The virtual multi-tape cartridge unit includes a housing having a hollow central cavity, the cavity further includes a central spool with magnetic tape spooled thereon. The central spool supplies magnetic tape to a tape drive subsystem during data processing operations. The magnetic tape has a number of parallel longitudinal data tracks defined thereon, wherein the data tracks are arranged into a number of track groups. Each track group has a logical beginning of media (BOM) field and a logical end of media (EOM) field positioned near respective ends thereof. The logical BOM and EOM fields uniquely identify each track group. Consequently, each data track group emulates a logical sub-tape cartridge that may be individually identified as well as selected for data processing operations thereon.