The database life cycle (DBLC) defines the stages involved for implementing a database, starting with requirements analysis and ending with monitoring and modification. Furthermore, the DBLC never ends because database monitoring, modification, and maintenance are part of the life cycle, and these activities continue long after a database has been implemented. Put simply, the DBLC encompasses the lifetime of the database. The five stages in the database life cycle are:
Monitoring, modification, and maintenance
The first three stages (1. Requirements analysis 2. Logical Design 3. Physical Design) are database-design stages, which are listed below the diagram shown above.
First Three Stages
Requirements Analysis: Requirements Analysis is the first and most important stage in the Database Life Cycle. It is the most labor-intensive for the database designer. This stage involves assessing the informational needs of an organization so that a database can be designed to meet those needs.
Logical design: During the first part of Logical Design, a conceptual model is created based on the needs assessment performed in stage one. A conceptual model is typically an entity-relationship (ER) diagram that shows the tables, fields, and primary keys of the database, and how tables are related (linked) to one another. The tables sketched in the ER diagram are then normalized. The normalization process resolves any problems associated with the database design, so that data can be accessed quickly and efficiently.
conceptual model: A description of the structure of a database. In this course, you will complete the tasks associated with "Requirements Analysis" and the first part of logical design, which is developing a conceptual model.
entity-relationship (ER) diagram: A diagram used during the design phase of database development to illustrate the organization of and relationships between data during database design.
normalization: The process of applying increasingly stringent rules to a relational database to correct any problems associated with poor design.
Physical Design: The Physical Design stage has only one purpose: to maximize database efficiency.
This means finding ways to speed up the performance of the RDBMS. Manipulating certain database design elements can speed up the two slowest operations in an RDBMS: retrieving data from and writing data to a database.
Before moving on to the next lesson, read the section below to learn more about the stages in the DBLC.
Description of the DBLC Stages
The five stages of the Database Life Cycle associated with each task:
The stages and the principal task associated with each are listed below.
Requirements analysis: identify business objects
Logical design: create a conceptual model
Physical design: tweak database for performance
Implementation: create SQL tables
Monitoring, modification, maintenance: update records
The Modern Database Life Cycle (DBLC) contains six phases:
database initial study,
implementation and loading,
testing and evaluation,
maintenance and evolution.
Database Initial Study
During the "Database Initial Study", the designer must examine the current system's operation within the company and determine how and why the current system fails. The overall purpose of the database initial study is to:
Analyze the Company Situation: The company situation describes the general conditions in which a company operates, its organizational structure, and its mission. To analyze the company situation, the database designer must discover what the company's operational components are, how they function, and how they interact.
Define Problems and Constraints: The designer has both formal and informal sources of information. The process of defining problems might initially appear to be unstructured. Company end users are often unable to describe precisely the larger scope of company operations or to identify the real problems encountered during company operations.
Define Objectives: A proposed database system must be designed to help solve at least the major problems identified during the problem discovery process. In any case, the database designer must begin to address the following questions:
What is the proposed system's initial objective?
Will the system interface with other existing or future systems in the company?
Will the system share the data with other systems or users?
Define Scope and Boundaries: The designer must recognize the existence of two sets of limits:
The system's scope defines the extent of the design according to operational requirements. Will the database design encompass the entire organization, one or more departments within the organization, or one or more functions of a single department?
Knowing the scope helps in defining the required data structures, the type and number of entities, the physical size of the database, and so on. The proposed system is also subject to limits known as boundaries, which are external to the system.
Boundaries are also imposed by existing hardware and software.
The next lesson provides an overview of the post-design stages of the DBLC.