Abstract: A method for managing Data Storage Medium (DSM) mount and demount decisions in an automated data storage library that dynamically optimizes both sequential and random data access workloads. The demount decisions adapt to time-varying characteristics in the relative workload mix. When the workload is primarily sequential, the mount and demount decision procedure favors longer mount residency for sequential access streams, reducing the robotic picker activity and reducing response time for mount requests. When the workload is predominantly random access, sequentially accessed DSM residency time is generally reduced and preemptive demounts are more readily implemented. The disclosed method provides for preemptive demounts and uses a two-element decision process to select either a Least Recently Used (LRU) or a Least Recently Mounted (LRM) decision parameter. The relative weights of the LRU and LRM decision tests are varied responsive to measured changes in data access workload characteristics.

Abstract: Fast formatting of DASD emulating sectors on optical media is provided to reduce initialization time. Rather than format each track media when a new surface of an optical media is mounted in an optical storage library, a table is created on the media containing a set of entries for each track on the media surface. During initialization, a first table entry for each track is set to indicate that the state of the track is reliably KNOWN and a second entry is set to indicate that the track is virgin (unrecorded). Prior to a subsequent data access operation, the track table is copied from the media into a corresponding table in memory and each first entry in the media table is changed to indicate an UNKNOWN state. The memory track table is updated during the data access operations to reflect newly recorded or updated sectors. Upon completion of the data access, the media table is overwritten with the updated memory table.

Abstract: A record media (optical disk) automatic library (back store) houses a plurality of record media for selective mounting in any one of a plurality of media drives (front store). Each record medium has one or more addressable recording surfaces termed data units. Record media currently mounted in said media drives may be replaced by other record media (demounted) only if the individual data unit has been idle (not accessed) for a time longer than a predetermined horizon time (demount eligibility threshold). If the current idle times for all mounted media are less than the respective horizon times, then no media can be demounted. Then, all proposed record media mounts are delayed until one of the currently mounted record media becomes eligible for demounting. If a plurality of mounted record media are eligible for demounting, then a least recently used one of the data units is demounted. The idle time of each mounted data unit is separately timed.