Database Reference
In-Depth Information
database into data sets on the basis of usage. If a fragment contains data that are
most relevant to one location, then that data set is kept at that location. At each
location, a fragment of the enterprise data is placed based on the usage.
Each fragment of data at every location may be managed with the same type
of database management system. For example, you may run Oracle DBMS at
every location. In that case, you run your distributed database as a homogenous
database. On the other hand, if you elect to manage the data fragments at different
locations with different DBMSs, then you run your distributed database as a col-
lection of heterogeneous database systems. Heterogeneous arrangement provides
extra flexibility. However, heterogeneous distribution is difficult to coordinate and
administer.
SURVEY OF THE DATABASE INDUSTRY
So far we have reviewed the basic concepts of the database approach. You have
understood the forces that drove the transition from file-oriented systems to
database systems. We discussed in detail how the escalating demand by organiza-
tions for information and the explosive growth of computing technology mutually
contributed to the rise of database systems. We also looked into the types of
databases.
We should now conclude with a brief survey of the database industry. Where is
the industry now? How did it get here? You will find such a survey useful because
it will provide you with the context and the foundation for further study. You have
been introduced to the leading data models. As you walk through a brief history,
you will grasp the significance of one data model following the earlier one. A list of
the leading commercial database management systems will give you an apprecia-
tion of the spread of database systems. You will also get a quick glimpse of the future
direction of database technology. We will be returning to these topics in later chap-
ters. At this stage, let us just do a brief survey.
Brief History
Although the initial movement toward database systems began in the 1960s, soft-
ware sophistication and widespread use of database systems began in the mid-1970s.
More and more organizations began to adopt database technology to manage their
corporate data. Figure 1-13 provides you with a historical summary of the database
industry. The figure highlights the major events and developments in the various
decades.
Generalized Update Access Method (GUAM) contained the first trace of the
forerunner to the hierarchical database systems. In early 1960s, Rockwell developed
this software to manage the data usually associated with manufacturing operations.
IBM picked this up and introduced Information Management System (IMS) as a
hierarchical database management system.
Integrated Data Store (IDS), developed at General Electric, formed the basis
for database systems on the network data model. Database Task Group (DBTG)
of the Conference on Data Systems and Languages (CODASYL) began to produce
standards for the network model. CODASYL, a consortium of vendors and
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