Tape library

[1] Some large application systems could require scores of different tapes as part of their batch job runs.

[2] In the data processing applications of the era, the master files for such things as employee payroll information, supplies and stores inventory, or customer accounts were typically kept on tape.

[1] The tapes representing a few past iterations of a master file would typically be retained, in case a problem with the latest version were to be discovered and the job had to be rerun.

[1][4] In this era, there were no automated tape delivery and mounting systems, and so this action had to be done by computer operators.

[1] Even careful computer operators could sometimes mount the wrong tape as input to a job or present the reels of a multi-tape dataset out of order.

[4] As one book of the era wrote, "keeping track of the whereabouts of the tapes is a formidable and responsible job.

Such capacity is multiple thousand times that of a typical hard drive and well in excess of what is capable with network attached storage.

[17] The tradeoff for their larger capacity is their slower access time, which usually involves mechanical manipulation of tapes.

Because of their slow sequential access and huge capacity, tape libraries are primarily used for backups and as the final stage of digital archiving.

[18] The term autoloader is also sometimes used synonymously with stacker,[19] a device in which the media are loaded necessarily in a sequential manner.