Building the Data Warehouse

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before image a snapshot of a record prior to update, usually placed on an activity log.

bitmap a specialized form of an index indicating the existence or nonexistence of a condition for a group of blocks or records. Bitmaps are expensive to build and maintain but provide very fast comparison and access facilities.

blocking the combining of two or more physical records so that they are physically located together. The result of their physical colocation is that they can be accessed and fetched by a single execution of a machine instruction.

cache a buffer usually built and maintained at the device level. Retrieving data out of a cache is much quicker than retrieving data out of a cylinder.

cardinality (of a relation) the number of tuples (i.e., rows) in a relation.

CASE computer-aided software engineering

checkpoint an identified snapshot of the database or a point at which the transactions against the database have been frozen or have been quiesced.

checkpoint/restart a means of restarting a program at some point other than the beginning for example, when a failure or interruption has occurred. checkpoints may be used at intervals throughout an application program. At each of those points, sufficient information is stored to permit the program to be restored to the moment in time the checkpoint has been taken.

CLDS the facetiously named system development life cycle for analytical, DSS systems. CLDS is so named because, in fact, it is the reverse of the classical systems development life cycle SDLC.

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