Abstract: A end report of the unloading operation is issue to a host computer for a period of time after the start of the ejecting operation of a medium cartridge of a recording/reproducing unit based on an unloading command until before the end of the unloading operation, thereby allowing the next moving command to be issued precedently to the end of the actual unloading operation. Simultaneously there for with that the unloading operation is instructed to the recording/reproducing unit on the basis of the unloading command, the end report of the unloading operation is executed to the host computer, thereby allowing the host computer to issue the next moving command. In a data transfer control between the host computer and a control unit of a library apparatus, when the number of error times of the data transfer errors exceeds a threshold value, the subsequent data transfer speed is switched to the executable data transfer speed at which the data transfer can be retried, and the data transfer is executed.

Abstract: Management information necessary to manage storage media in a mass storage system. A rotatable cell drum has a plurality of cells arranged in a plurality of cell columns disposed in spaced circumferential relationship parallel to the axis of the drum and in a plurality of shelves disposed in spaced relationship transverse to the axis of the drum. A housing of the cell drum has an opening which confronts N cell columns of the cell drum, wherein 1.ltoreq.N< the desired number of cell columns, thereby to enable manual storage of a storage medium in, or retrieval of a storage from, a corresponding cell in the N cell columns made accessible through the opening in the load/eject mode of operation of the mass storage system.

Abstract: A end report of the unloading operation is issued to a host computer for a period of time between after the start of the ejecting operation of a medium cartridge of a recording/reproducing unit based on an unloading command until before the end of the unloading operation, thereby allowing the next moving command to be issued precedently to the end of the actual unloading operation. Simultaneously with that the unloading operation is instructed to the recording/reproducing unit on the basis of the unloading command, the end report of the unloading operation is executed to the host computer, thereby allowing the host computer to issue the next moving command. In a data transfer control between the host computer and a control unit of a library apparatus, when the number of error times of the data transfer errors exceeds a threshold value, the subsequent data transfer speed is switched to the executable data transfer speed at which the data transfer can be retried, and the data transfer is executed.