Database Reference
In-Depth Information
What has happened in the business scene since then? More and more corpora-
tions have become global in their operations. Business opportunities outside the
local areas have provided growth and profitability. Think of the local bank where
you opened a checking account about 10 years ago. To survive and be profitable,
the bank has probably extended into a few more states and perhaps has even
become international. Let us say that your progressive bank has become global and
has opened branches in London, Paris, Tokyo, and Hong Kong in addition to a large
number of domestic offices. The Paris branch primarily serves French customers.
The users in the Paris branch access the data from the bank's database. But most
of the data they need is about the local customers. Does it make sense for the Paris
branch to go all the way to the centralized database stored in New York to access
data about French customers?
All organizations expanding through mergers, acquisitions, and consolidations
because of competitive pressures face similar questions. Each local office seeks
autonomy, data ownership, and control for better service to its customers. The trend
is to distribute the corporate data across the various dispersed locations so that each
location can efficiently access the data it needs for running its portion of the overall
business. This pattern of decentralization is not the same type of decentralization
that existed in the case of the old file-oriented system. At that time, the decentral-
ization based on applications perpetuated dispersal of redundant data with no infor-
mation sharing. What you observe now is different. Database is being decentralized
with geographic separation of data, but logical unity and integrity are preserved for
proper information sharing—one logical database, but data not stored in just one
location.
How is this becoming possible? Distributed database systems are emerging
as a result of the merger between two major technologies: database and network.
Recent advances in data communications and standardization of protocols such
as Ethernet, TCP/IP, and ATM, along with the ubiquity of the Internet, promote
physical distribution of corporate data across global locations yet preserving the
integration and logical unity.
Database vendors have not yet come up with “pure” distributed database systems
as envisioned in research studies. The technology is slowly maturing. Vendors
are developing systems based on the client/server approach and the concept of a
collection of active heterogeneous, geographically dispersed systems.
But the
momentum is strong and sustained.
FUNDAMENTAL PRINCIPLES
How is the push for decentralization of corporate data to be accomplished?
Remember, the storing of relevant portions of the data has to be at each of the
various geographic locations; but at the same time, users at each location must be
able share data with users at any and all of the locations. Physical separation but
logical integration—that is the underlying premise.
Examine this premise. What this implies is that when a user executes a query or
a transaction accessing some data from the database, the user must be able to do
so without knowing where the data resides and how it is going to be retrieved. The
distribution of the data across the locations must be transparent to the user. The
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