Data Storage Redundancy COBRA
Oracle Tips by Burleson Consulting
High Performance Data Warehousing
Early Disk-Based Data Storage
* Data relationships could not be maintained.
Early flat-file systems could not easily recognize and manage the
natural relationships between data items. One-to-many and
many-to-many data relationships were often ignored, and widespread
denormalization of the data occurred.
* "Islands of information" developed within organizations, as
different departments developed independent flat-file systems. These
departmental "islands" were often written in different programming
languages, with different file structures, and it was very difficult
for a department to share information with other departments. (See
* Widespread data redundancy developed. Each department within the
corporate database often duplicated information, leading to the
increased costs of data storage, and the possibility of update
anomalies when an item was changed within one department but not
* Maintenance nightmares ensued. Because these systems had no
repository of metadata, program changes became very cumbersome.
Whenever a file changed in structure, the programs which referred to
the file could not readily be identified, and every program which
referenced that file had to be modified and recompiled.
* Tightly-coupled data and programs led to maintenance problems.
Because many application programs defined and maintained their own
data structures, there was a problem as all new programs were forced
to adhere to the calling procedures of the existing programs. The
same communications problems exist within object-oriented systems.
The Common Object Request Broker (CORBA) standard for
object-oriented systems was designed to insure that this problem
will not resurface in the future.
* No concurrency control or recovery mechanisms. Systems had no
method for simultaneously updating information and no way to
roll-forward information in case of disk failure.
* No method for establishing relationships between data items. The
relationships between data items are generally lost or introduced
with cumbersome data structures, such as repeating fields within
Figure 1.4 Islands of information.
This is an excerpt from "High Performance
Data Warehousing", copyright 1997.
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