Database Reference
In-Depth Information
ual data views, and the internal schema to define the storage spaces and to tie the
data structure to physical storage.
Populating the Database
What has taken place so far in the database development life cycle? The require-
ments definition was completed, and the requirements drove the subsequent phases.
The logical design activities were finished. The logical design was translated into the
physical design. The data dictionary files have been built. The storage space is ready.
The data dictionary has all the entries necessary to define the data structures and
relationships. What next? Next comes the activity of placing data in the database so
that users can make use of the data.
You place data in the database in two stages. Is your database being converted
from some other data system? Are you making the transition from a file-oriented
data system? Or are you converting to a later database model? In any case, you will
have to convert the data over to the new database system. This is the initial loading
of data. Initial loading is usually done through utility programs provided in the
DBMS package. Some organizations may opt to load initial data by using third-
party tools. Generally, populating the database consists of the following major tasks:
•
Extract data from the old data system and create extract files.
•
Verify extract files for correctness and data consistency.
•
Prepare data in the extract files by sorting and merging as needed.
•
Create load files from the sorted and merged extract files to conform to the
target database structures.
•
Use DBMS load utility or third-party utility programs to populate database
with initial data.
Developing Application Interfaces
Loading initial data is the first activity for placing data in the database. This is just
the initial data from the old system. Once the database is up and ready for use, day-
to-day business transactions can begin to store data in the new database. Ongoing
transactions may add, update, or delete data from the database. This is the next
activity in populating databases. Users now take over the task of manipulating data.
However, users need applications designed and built to be able to access data from
the database. The applications needed to run the business processes must have inter-
faces to connect to the new database. Although applications may be thought of as
part of the overall database environment, design and development of applications
fall outside the scope of DDLC. The DDLC phases cover the design and develop-
ment of databases; application design and development is usually accomplished
through a similar life cycle approach—system development life cycle (SDLC).
MAINTENANCE AND GROWTH
The database development life cycle (DDLC) does not end with deployment of the
database system and the users beginning to use the system. The development life
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