A method of accessing a multifile storage medium and a library system. The library system includes recording/reproducing apparatuses for performing a recording/reproducing operation on the multifile storage medium, a plurality of recording/reproduction control units for controlling transaction of information with a host, a plurality of buffers provided between the recording/reproduction control units and the recording/reproducing apparatuses, a library control unit for controlling the whole library system, a directory for recording correspondence between the individual multifile recording media and a plurality of files stored therein, a shelf for housing the multifile storage media and handling devices. The plural buffers can be accessed independently of one another. Plural files are transferred between the buffers and the storage medium on a file-by-file basis. The access requests to the files are disposed of within the buffer.

In a disc apparatus, past access records concerning data items stored in the optical disc apparatus and exchange records of optical discs are managed, and access frequencies in the future are estimated on the basis of these records. Data items estimated to be accessed at a high frequency are stored into a cash HDD as a high-speed device, and data items estimated to be accessed at a middle frequency are collected into a specific optical disc. This specific optical disc is continuously installed in an optical disc drive. As a result, the response ability of the apparatus is greatly improved.

A dynamic process for improving the performance of a tape-based storage system is disclosed which takes a global view with regard to scheduling and tape selection. All requested data blocks located on multiple tapes within the storage system are analyzed and, taking advantage of the existing replication of some of the requested data blocks on multiple tapes and the location of the data blocks on the tapes, a schedule is formed that results in the reading/downloading of requested data blocks in an efficient manner.

The cache memory is divided into a plurality of slots, each of which is used to store data files that are staged from the storage devices for transmission to the processor or received from the processor for writing on the storage devices. The management of the plurality of slots is accomplished by the use of at least two sets of lists: global lists and local lists. These lists function to respectively manage the entirety of the cache memory and the slots, either on an individual slot basis or on a virtual device basis. These two sets of lists therefore operate on a substantially orthogonal basis, while also operating cooperatively, to efficiently manage the writing of data into and out of the cache memory.

In an automatic library system for transportable data storage units, a library storage control reduces the chances of contention for file mounting. The magnetic tape library system 3 includes first read/write apparatus 20 with automatic mounting and second read/write apparatus 30 not requiring automatic mounting. Depending on the utilization of the first read/write apparatus 20, write data is recorded temporarily in a common storage installed in the second read/write apparatus 30. When the utilization of the first read/write apparatus 20 is low, the temporarily stored data is automatically transferred to a data storage unit in the first read/write apparatus 20 in which the data should normally be stored. The handlers and the first read/write apparatus 20 can be used with priority for handling data storage units for read data that require transport from the storage shelf or holder. The apparent number of the read/write apparatus increases by an amount equal to the number of data writes, improving the system throughput.