One of the more important reasons an installation purchases any data storage management system is to minimize the amount of DASD space allocated to data sets that are rarely or never accessed. The amount of DASD space allocated can be accomplished in CA Disk by both explicit and implicit archival, based on last used date. Typically, the more constrained an installation is for DASD space, the shorter the time allowed for a data set to be unused prior to archival. As the unused time window shrinks, more data sets are archived that do get accessed infrequently. This is especially common for data sets that get referenced only on a monthly or yearly basis.
Although this archival scheme accomplishes one of the DASD manager's primary functions--ensuring enough DASD free space exists for day-to-day operations--it can also create a less than amicable relationship with the data center's users if not implemented properly. For example, if a system is set up to archive all data sets not used within two weeks, those data sets that are only accessed once a month are archived between each job cycle.
The user must either respond to this problem by restoring all required data sets prior to a job run, or artificially referencing the data sets periodically to avoid having them archived. In the first case, an extra workload is created for the user, and in the second case the DASD manager is prevented from doing an effective job. Although the DASD manager could exempt these data sets from being archived by CA Disk, this cannot be a good alternative since the data sets could then remain on DASD long after the system that uses the data sets is removed from production. And if an installation is critically short of free DASD space, it cannot have the luxury of letting seldom- used data sets tie up valuable DASD space between job cycles.
An automatic restore capability helps to solve this potential conflict between the DASD manager and the end user by allowing data sets to be archived by the DASD manager and then restored automatically by CA Disk if they are required by an application later. This solves the DASD manager's problem of keeping free space available and also relieves the user of the burden of restoring required data sets before cyclical job runs.
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