Given
the low reliability of the target environment, we also show how replicas are incorporated
in the design of a robust NPDW strategy with availability guarantees and
how the replicas are used for always-on, always efficient behavior in the presence
of periodic load and maintenance tasks.
204 Furtado
Copyright ?© 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of
Idea Group Inc. is prohibited.
Introduction
Data warehouses (DWs) are specialized databases storing historical data pertaining
to an organization. The objective is to allow business analysis on varied perspectives.
They have been applied in many contexts, for instance, insurance companies
keeping track of individual events on insurance policies, telecom companies with
terabytes of data tracking individual phone calls or individual machine events in
production factories, generating gigabytes of detailed data per day. The degree of
detail over which the data is stored in the data warehouse can vary, but from the
examples given, it is easy to see that data warehouses can become extremely large.
As such, multiple performance optimization strategies can be sought after, ranging
from specialized indexing, materialized views for faster computation over predicted
query patterns, to parallel architectures and parallel processing.
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