The Relational Database Lifecycle - Essay Example

Relational Database Application Lifecycle The relational database lifecycle is the process through which a relational database system is developed. Within the larger information system, the database, too, is subject to a life cycle. The Database Life Cycle contains six phases: initial study, database design, implementation and loading, testing and evaluation, operation, and maintenance and evolution. (Rob & Coronel, 2002) 1. The Initial Study The initial study is conducted to identify and clarify the scope and initial estimate for time, cost, and the need for the system. So, in addition to examining the current system's operation within the company, the designer must determine how and why the current system fails and gather information and other requirements for the new system. The overall purpose of the database initial study is: Analyze the company situation. Define problems and constraints. Define objectives. Define scope and boundaries. 2. Database Design The second phase focuses on the design of the database model that will support company operations and objectives. In the process of database design, concentration must be placed on the data characteristics required to build the database model. Two views of the data within the system are available the business view of data and the designers' view. RDBLC's second phase also includes data definition. It is also important to note thatthe database design is not a sequential process it is rather an iterative process with continuous feedback. The database design of the RDBLC can be further broken down into sub design components I.Conceptual Design In the conceptual design phase, an abstract structure is created that represents real-world objects in the most realistic way possible. The conceptual model must represent a clear understanding of the business and its functional areas and is software and hardware independent. The conceptual model design requires three steps: i) Data analysis and requirements (determining the data element characteristics) ii) Entity relationship modeling and normalization (The ER model serves to be a communication tool between technical and non-technical individuals as well as a design blueprint. During normalization the dependencies are checked and data anomalies removed) iii) Data model verification (The ER model must be verified and validated against the planned system processes) II. Logical Design Logical design is used to translate the conceptual design into the internal model (database schema) for a selected database management system. Therefore, the logical design is obviously software-dependent. III. Physical Design Physical design is the process of selecting the data storage access characteristics of the database. These characteristics are actually the types of devices supported by the hardware, the system, and the DBMS. Therefore the physical design is hardware dependant. It affects not only the location of the data in the storage device(s) but also the performance of the system. 3. Implementation and Loading The relational database and its interfaces are created according to the specification of a logical schema. A new database implementation requires the creation of special storage-related blocks for the placement of end-user tables. During the implementation and loading phase, the security, performance, integrity, backup and recovery, standards, and control issues must also be addressed. 4. Testing Once the data have been loaded into the database, the DBA tests and fine-tunes the database for performance, integrity, concurrent access, and security constraints. The testing and evaluation phase occurs in parallel with applications programming. 5. Operation Once the database has passed the test phase, it is considered to be operational. On the whole all the components the database, its management, its users, and its application programs are in place at this time and represent a complete information system. 6. Maintenance The maintenance phase starts as soon the database is implemented. The database administrator must be prepared to perform routine maintenance activities within the database such as: Preventive (periodic maintenance of the database including backup). Corrective maintenance (correcting errors and recovery of the database). Continuous improvement/changes (enhancing performance, restructuring the database by adding or subtracting entities and/or attributes). Performing database audits based on security policies and the system-generated statistics. (Rob & Coronel, 2002) General RDBMS Architecture Generally speaking the database architecture can be viewed as a three layered architecture (also called Garlan & Shaw layered architecture) at the highest level of abstraction. The three main components are shown in the following diagram: Application Layer The application layer serves to be the interface for all the users of a system. Generally, users can be categorized into any of the four categories given below: 1. Sophisticated - who have a high level of knowledge with respect to databases and scripting languages and interact with the system without any application by forming their requests directly with database query language. 2. Specialized - those users are application developers who create the required database applications. 3. Naive - the day-to-day, basic level users who interact with the system with the help of applications already developed. 4. Database Administrators who have complete control over the entire database system. The database administrator's tasks are as follows: Deployment: Database Installation and configuration (databases, stored procedures, e.t.c) Database Loading (initial content) Fine tuning the database Operations: Database Administration including: Ensure Database Characteristics. Ensure that each database has the required characteristics: Ensure operational availability and minimum required database performance. Ensure and maintain required levels of database security. Ensure the databases are functioning properly (all the hardware and software resources included). Administer Databases. Administering the database includes: Installing the databases. .Loading the data into the databases. Backup database contents. Upgrade and maintain the database management systems Rollback database contents. Documentation. Record and maintain database-related documents such as: Installation Manual Deployment Plan Operations Log Operations Manual Maintenance. Apart from the regular up-keep this includes, Defect Identification, Defect Correction and Defect Status Reporting. Logical Layer The logical layer represents the core functions of the RDBMS. At the highest level of abstraction four important modules can be distilled from the logical layer and this portion of the system that utilizes a wide variety of vendor specific implementations. The diagram also shows the general control flow between the modules. (Harrington, 2002) Physical Layer The RDBMS stores a variety of information in secondary storage and it is accessed via the storage manager. The main types of data kept in the system are: Data dictionary - stores metadata (information about the structure of the database) Data files - which store user data Log Information - keeps track of executed queries. The logs can then be used to successfully recover the database in the event of a system crash. Indices - provide speedy access to data items having particular values Statistical Data - store statistical information about the data in the database for efficient query processing (Harrington, 2002) References: 1. Peter Rob & Carlos Coronel. 2002. Database Systems, Design, Implementation, & Management; Fifth Edition. 2. Jan L. Harrington. 2002. Relational Database Design Clearly Explained, Second Edition. Read More