What is Functions of DBMS
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Functions of DBMS
Some important functions of DBMS are as follows:
1. Data Processing
The most important function of DBMS is data processing. It includes the creation, storage, and arrangement of data in the database. DBMS also provides access to data stored in databases.
2. User-accessible Catalog
A catalog is an object that contains all information about the database. It includes schema information, user information, user rights, etc. The administrative user of the database should be able to access the catalog. It is an important function of DBMS to provide access to the catalog.
3. Transaction Support
A collection of all steps to complete a process is known as a transaction. DBMS should support transactions. It must ensure that all steps in a transaction are executed successfully or none of them is executed. This facility ensures that the database is always inconsistent state even if a transaction fails due to some problem such as system crash or power failure etc.
4. Concurrency Support
A situation in which two or more persons access the same record simultaneously is called concurrency. This situation may result in loss of information or loss of integrity. DBMS must provide the facility of concurrency. It enables multiple users to access the same record simultaneously without any loss of data.
5. Recovery Services
A DBMS must provide a mechanism to recover a database if it is damaged in any way. It ensures that the database remains in a consistent state. DBMS must also ensure that data loss during the recovery process is minimum.
6. Data Communication Support
DBMS must provide data communication support in different ways. It must be capable of integrating with communication software. The users usually access the database from workstations. The workstations may be connected to the host computer or located at distant locations. The workstations communicate with the host computer over a network. DBMS receives their requests as communication messages. All communication is handled by Data Communication Manager (DCM). The DCM is not part of DBMS but the DBMS should be
capable of integrating with DCM for data communication.
7. Integrity Services
Integrity means accuracy and reliability of data. It is maintained by applying particular constraints on the data. Data integrity rules ensure the correctness and consistency of stored data. DBMS must provide integrity services to maintain the integrity of data. It must protect the database from false and incorrect data.
8. Authorization Services
DBMS must ensure the security of the database through authorization services. It should ensure that only authorized users can access the database. The authorization is normally implemented with the help of passwords etc. DBMS must also provide different levels of authorization. For example, one user may be authorized to access the full database but another user may be allowed to access only a part of the database.
Database Development Process
The development of a complete database application is a lengthy and complicated process.
Different strategies can be used to develop database applications which are as follows:
General Strategies
A database application is developed to satisfy the requirements of the user. It is very important to understand these requirements in detail. The application should be developed according to the expectation of the user. Different techniques are used to find the requirements and needs of users such as interviews. The requirements should be defined as early as possible in the development process. There are two strategies to develop a database application:
1. Top-Down Development
2. Button-up Development
1. Top-Down Development
This strategy starts with general issues and moves to specific issues. First of all, it is important to find out the general goals of the organization and the means by which these goals can be achieved. The requirements are defined that must be satisfied to reach these goals. This study gives an abstract data model of the system. The user moves to detailed and specific issues using this model. This process identifies a particular database and related application to be developed. Finally, the high-level data model is transformed into low-level models. All identified systems, databases, and applications are developed.
2. Bottom-Up Development
This strategy starts with specific issues and moves to general issues. The user begins by
identifying a specific system to be developed. The requirements are found by studying the
existing system and by interviewing different users.
