Abstract: A data storage library efficiently utilizes I/O slots while maintaining software compatibility by using functional addresses to conduct virtual cartridge moves from storage slots to I/O slots. More particularly, a location-centric library host manages cartridge movement according to functional storage addresses and functional I/O addresses. In reality, the library has multiple cartridge receiving slots, which include physical I/O slots and physical storage slots. In contrast with the physical I/O slots and physical storage slots, functional I/O addresses and functional storage addresses are virtual locations used by the host in managing cartridge locations. Thus, host knowledge of cartridge locations is limited to their functional addresses. The library includes a library map that correlates functional addresses with physical addresses. Initially, an eject command is received from the host.