Building the Data Warehouse

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It is interesting to speculate what the world of information processing would look like if the only medium for storing data had been the magnetic tape. If there had never been anything to store bulk data on other than magnetic tape



master files, reports




lots of master files !!!

•    complexity of—

•    maintenance

•    development

•    synchronization of data

•    hardware




database—“a single source of

data for all processing”

tx processing    MIS/DSS

online, high-performance transaction processing

PCs, 4GL technology

the single-database-serving-all-purposes paradigm

Figure 1.1 The early evolutionary stages of the architected environment.

files, the world would have never had large, fast reservations systems, ATM systems, and the like. Indeed, the ability to store and manage data on new kinds of media opened up the way for a more powerful type of processing that brought the technician and the businessperson together as never before.

The Advent of DASD

By 1970, the day of a new technology for the storage and access of data had dawned. The 1970s saw the advent of disk storage, or direct access storage device (DASD). Disk storage was fundamentally different from magnetic tape storage in that data could be accessed directly on DASD. There was no need to go through records 1, 2, 3, … n to get to record n + 1. Once the address of record n + 1 was known, it was a simple matter to go to record n + 1 directly. Furthermore, the time required to go to record n + 1 was significantly less than the time required to scan a tape. In fact, the time to locate a record on DASD could be measured in milliseconds.

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