A technique for recalling data objects stored on media. A queue is created
for each medium on which data objects are located, where each request to
recall a data object is placed on the queue corresponding to the medium
on which the data object is located. A queue is "active" when its
corresponding medium is mounted and being used for recall; otherwise the
queue is "non-active." A thread is created for each active queue, where
the thread retrieves from a medium the requested items on the active
queue. When plural drives are available for mounting and reading media,
plural queues may be active concurrently, so that the plural queues'
respective threads may recall items from the plural media in parallel.
Preferably, the requests on each queue are organized in an order such
that the offset locations of the requested items form two monotonically
increasing sequences.