The Database Life
Cycle
The following common
sense principles must be considered during the design and implementation of any
database:
?
Determining the need for a
system
?
Defining the goals for the
system
?
Gathering business
requirements
?
Converting business
requirements to system requirements
?
Designing the database and
application interface
?
Building, testing, and
implementing the database and application
These principles are applied by most database design methodologies.
A methodology is a set of guidelines for designing a database.
The Barker method is
one of the most common methodologies used for relational databases, and involves
the following seven phases:
??????????? 1.???????? Strategy
??????????? 2.???????? Analysis
??????????? 3.???????? Design
??????????? 4.???????? Build
??????????? 5.???????? Documentation
??????????? 6.???????? Transition
??????????? 7.???????? Production
Strategy involves
planning the design effort.
In the analysis phase,
the development team interviews key employees to gather all the business
requirements - which will be used as a model for the system.
During the design
phase, a physical model is designed based on the logical model that was designed
in the analysis phase.
After the design is
complete, the database is built.
The use of
documentation is extremely beneficial, both for system users and application
users.
During the transition
phase, data is prepared to be moved into the production environment. The
end-user application is tested against the database with real data to ensure
that all components of the application function properly and that the integrity
of the data as stored in the database is consistent.
Finally, the database
is ported into a production environment, where it is available to the end user
for daily use.
The following figure
outlines the 7 phases of the Barker method:
A
design methodology may be adapted to meet an organization?s
needs.
The Oracle Designer
adapted design method is outlined in the following steps:
??????????? 1.???????? Strategy
??????????? 2.???????? Pre-analysis
??????????? 3.???????? Analysis
??????????? 4.???????? Pre-design
??????????? 5.???????? Design
??????????? 6.???????? Build
??????????? 7.???????? Test
??????????? 8.???????? Implementation
??????????? 9.???????? Maintenance
Maintenance?is a huge part of the life of most information
systems.
After a system has been
designed, tested, and implemented, it must be maintained for the remainder of
its life.
Maintenance includes
performance tuning and change management.
Two levels of system
maintenance that must occur are as follows:
? 1.????????
Database maintenance?-
Involves the maintenance of the back-end database, related mainly to how data is
stored in the database and how it grows after a given period of time. When new
data is created in the database and old data is deleted, fragmentation occurs.
One of the main tasks during database maintenance is to monitor the usage and
growth of the database, and keep fragmentation to a minimum. Also, it is
important to tune the database after it has been implemented to attempt to
improve overall performance for the end user. Changes that might occur to a
database throughout its life include the addition or deletion of database
tables, columns, or indexes. It might be necessary to change any piece of the
database structure as business and user needs change. Change requests are
usually provided by the end user or the development team if an application
change is also being made. Changes are implemented by the development team and
the database administrator. Database maintenance is performed by the database
administrator.
? 2.????????
Application maintenance?-
Involves the ongoing maintenance of an application after it has initially been
made available to the end user. Performance tuning an application might be
related to the way the application accesses objects in the database. One of the
most common performance problems associated with an application involves the
underlying SQL and programming code. There are many ways to write code to
perform the same task. For example, if a window in the application that reads
the database retrieves data slowly on a consistent basis, the SQL query behind
the window should be examined and tuned if necessary. Change requests are
usually provided by the end user. Application maintenance is performed by
application developers, although changes to the application might sometimes be
recommended by the database administrator.
Overview
of the Database Life Cycle
The database life cycle starts with a
requirement to have information available for the operation of a business.
The company begins to
plan for this proposed database, and resources are allocated for its
development.
There are several
reasons that provoke the need for a database.
Likewise, the need for
a particular database implementation might perish for additional reasons. Some
of these reasons are:
?
The
company changes the way it does business.
?
New
technology renders the existing database obsolete.
?
An
existing database needs to be re-engineered, but the costs would be far greater
than designing a new database because of the volume of revisions
involved.
The following database
environments are associated with the life of a database:
?
Development
?
Test
?
Production
The
following figure illustrates these environments:
Following is a
development evaluation checklist?that might assist in determining if a database
is ready to be tested:
?
Are all processes reflected
in the application?
?
Are all business entities
accounted for in the database?
?
Do all data elements and
processes defined allow new records to be entered?
?
Do all data elements and
processes defined allow existing records to be modified?
?
Do all data elements and
processes defined allow existing records to be deleted?
?
Do all data elements and
processes defined allow existing records to be queried?
?
Are all table relationships
accurate?
?
Has referential integrity
been applied?
?
Have obvious indexes been
created?
?
Have views been created
where needed?
?
Does the database need to be
normalized?
?
Have all errors been
accounted for and corrected during object creation?
The following test
evaluation checklist?might help determine if a database and
application has been properly tested and if it is time to make the transition to
production:
?
How much time has been
allocated to test the system?
?
When is the system expected
in production?
?
Do any data relationships
need to be modified?
?
Are business rules being
followed?
?
How did the database
application interface perform?
?
Was the system tested with
real data?
?
Was the system tested with a
realistic volume of data?
?
Was data integrity
compromised during testing?
?
Were all changes tested
thoroughly?
?
Was the database queried
after changes were made to data using the application interface (using a
combination of the application and manual transactions and queries to ensure
that the application is working properly)?
?
Have all requirements for
the system been double-checked for completeness?
The following
production evaluation checklist?might assist in the evaluation of a recent
implementation, as well as the decision to make modifications in attempt to
improve the system:
?
Were there any errors during
implementation?
?
Does the end user have any
complaints?
?
How does the system seem to
perform?
?
Was all live data loaded or
converted successfully?
?
What is the average number
of concurrent users?
?
Are any areas for immediate
improvement in database functionality or performance
recognized?
?
Are any areas for immediate
improvement in application functionality or performance recognized?
The
following figure illustrates possible problems if database changes are not
properly tested between versions:
