Editing Tape library (section)

=== Tapes and batch processing ===
In the [[mainframe computer]] era, especially the [[IBM mainframe]], the most common format in use was the [[9-track tape]].<ref name="popkin-pike"/>
Some large application systems could require scores of different tapes as part of their batch job runs.<ref name="mccracken"/>

In the data processing applications of the era, the [[master file]]s for such things as employee payroll information, supplies and stores inventory, or customer accounts were typically kept on tape.<ref name="mcquillen"/><ref name="stern-stern"/>  Batch jobs to update these master files would take the existing tape master file as input and write out a new tape master file as output.<ref name="ashley-fernandez">{{cite book | title=Job Control Language: A Self-Teaching Guide | first1=Ruth | last1=Ashley | first2=Judi N. | last2=Fernandez | publisher=John Wiley & Sons | location=New York | date=1978 | isbn=0-471-03205-0 | page=43 }}</ref> In addition, the set of update transactions themselves might constitute a second input tape.<ref name="mcquillen">{{cite book | title=System/360–370 Assembler Language (OS) | first=Kevin | last=McQuillen | publisher=Mike Murach & Associates | location=Fresno, California | date=1975 | lccn=74-29645 | page=302}}</ref> The master file output of one update job would then be the master file input to the next time the job is run, perhaps a day, a week, or a month later.<ref name="popkin-pike"/> 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.<ref name="popkin-pike"/>