What is Database Management?
Manual database management system has long been in use for recording and maintaining the data of an organization, prior to the advent of electronic database management systems. However, the manual system had various shortcomings.
To begin with, all the data and records were entered manually into the system, which was error-prone and led to lots of human errors. Secondly, multiple copies of the same data had to be maintained related to different departments of an organization, which led to the redundancy of data.
The redundancy of data makes it error-prone because, in case of updation, the data might get updated in one place and might get overlooked in the other, leading to discrepancies in the system. Thirdly, searching for particular data manually in the registers proved to be a time-consuming process.
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Database Management System (DBMS) emerged as an electronic solution to all these preceding problems. In DBMS, data is recorded and maintained electronically in the database, and the features of DBMS make data maintenance tasks easy to handle.
Thus, while a database refers to a collection of related data and information, DBMS refers to a collection of software and hardware systems that help in maintaining, managing, and querying the data stored in the database.
DBMS has the following characteristics:
- Enables creation of database and allows addition and deletion in database files
- Allows addition, deletion, and modification of data in the database
- Ensures easy retrieval of data collectively or selectively
- Enables sorting of data stored in the database
- Allows manipulation of data stored in the database by applying various mathematical functions
- Provides functionality for the generation of various reports required by an organization
- Maintains data consistency and data integrity by removing ambiguities throughout the database and thereby controls redundancy of data
- Enforces rules on the data as defined by users
- Enables sharing of data among different users
- Provides backup and recovery procedures to ensure there is no data loss in case of system failure
- Maintains a central repository of data, so that data can be controlled centrally
- Supports data manipulation and provides user-friendly interfaces to users to access and manipulate data easily
- Provides data abstraction, i.e., hides the unnecessary intricacies of how the data is stored in the database from users
- Ensures data security, so that no unauthorized user might access the private data of an organization
Objectives of Database Management
DBSM or database management has been developed while keeping a few objectives in perspective. These objectives have been in place to ensure ease of data storage and retrieval, and to provide a user-friendly interface.
A DBMS has the following objectives, as depicted in Figure:
Let us discuss these objectives further:
- Physical Independence
- Logical Independence
- Ease of Use
- Speed of Access
- Centralized Administration
- Limiting Redundancy
- Integrity Verification
- Data Sharing
- Data Security
Physical Independence
This signifies that the physical level is kept separate from the conceptual level and may be modified independently of the latter. This means that the user does not need to see all the hardware components of the database, which is simply hidden from the user’s perspective.
Logical Independence
This signifies that the conceptual level can be edited without disrupting the physical level. In other words, the database administrator must be able to make changes in the database without affecting the user’s interface.
Ease of Use
This refers to providing a user-friendly approach. Even users who are not familiar with the details of database management must be able to describe their query without referencing the technical aspects of the database.
Speed of Access
This refers to the speed with which data can be accessed from the database. The DBMS must be able to provide the result to user queries as fast as possible. DBMS utilizes algorithms i.e. pre-defined functions to enhance the speed of searching data in the database to obtain this objective.
Centralized Administration
This refers to the database administration handled by a database administrator centrally. DBMS enables users to retrieve, add, and update data; and verify its integrity in a centralized manner. The data is stored and managed centrally, thus, all the users have access to the same data, and there is no discrepancy in the data used by different users.
Limiting Redundancy
This refers to reducing the redundancies of data in a database. Data is stored centrally, thus, it ensures minimizing errors on any updations and also prevents wastage of memory. The DBMS has this inherent feature to be able to avoid redundant information whenever possible.
Integrity Verification
This refers to enforcing and maintaining the integrity of data. The data must be internally coherent, and when some elements reference other elements, referential integrity must be enforced.
Data Sharing
This refers to data sharing between different departments of an organization. DBMS is able to share the same data with multiple users and provide them with real-time access to the database.
Data Security
This refers to maintaining the security of the database by authorizing users by granting them access rights. DBMS is capable of managing each user’s data access rights and checks them against any random intrusion by unauthorized users.
Functions of Database Management
DBMS involves various functions that are vital for successful database management. Based on the functions incorporated in a DBMS, the selection of a DBMS is made. There are various DBMSs provided by different vendors in the market such as Oracle, Sybase, and Microsoft. A choice is made on the basis of the functions provided by each.
DBMS has some standard functions, which are shown in Figure:
- Physical Independence
- Logical Independence
- Ease of Use
- Speed of Access
- Centralized Administration
- Limiting Redundancy
- Integrity Verification
- Data Sharing
- Data Security
A database would not be able to work effectively without any of the functions shown in Figure. Each of these functions plays an important role in database management.
Let us discuss the major functions of DBMS further:
Retrieve and Update Data
It is the main function of a DBMS. Retrieving data is taking out the data from the database on the basis of user requirements. It is the most important and indispensable function of database management. Updating data in a database includes adding new records, deleting existing ones, and changing data within a record.
It is not necessary for the user to be aware of how DBMS carries out these functions, but he/she needs to be aware of when and how to query/update the data from the database.
Support Concurrent Updates
DBMS supports concurrent updates, so that important data is not lost or inaccurate. It is important when data is stored in multiple places. If that data is updated in one place then its copy elsewhere in the database needs to be updated too. Also, if multiple users are updating the database simultaneously, then these updates must occur simultaneously.
There are various features of DBMS, such as locking, two-phase locking, and time stamping methods, which are used by DBMS to support these concurrent updates and ensure that the updates are done accurately. The DBMS is responsible for the proper storage of updates.
Recovery of Data
It refers to one of the most important security-related functions of DBMS. In case of a system failure, i.e., a computer crash, a fire, or a natural calamity, DBMS is able to recover the database, so that the data is not lost. A system crashes may also occur if a user might enter incorrect information, invalidating or making records inconsistent.
In this scenario, if a database is destroyed or damaged in any way, the DBMS must be able to recover the previous correct state of the database, and this process is called recovery. The easiest way to achieve this is to take regular backups of data.
These regular backups can be scheduled for a set time so that in the case of a disaster, the database can be restored to a previous stable state.
However, any data or changes made after the last backup would be lost, which can prove to be problematic. To counter this problem, DBMS has a feature called Journaling. Journaling involves keeping a log of all the updates made to the database.
It is maintained in a file separate from the database and can be used to re-update the database up to the last update after it is recovered from the backup.
Data Security
Providing security to the database is a very significant feature of DBMS. It ensures that no unauthorized users are allowed to access the database without proper permission. DBMS uses features, such as encryption, authentication, authorization, and views, to provide security to the database. An unauthorized person is not given permission to access any data from the database.
Authentication involves providing all authorized users with unique IDs and passwords so that the database administrator can identify the person accessing the database using these parameters. If a password is not entered correctly, a user is denied access.
Authorisation is a set of rules that are defined by the Database Administrator (DBA) to specify levels of access that an individual or a group is allowed. Some users may only be allowed to view data, while others may be allowed to view/make changes in it.
Data Integrity
Data integrity provides a set of rules to ensure that incorrect or inconsistent data is not entered in the database. There are various types of integrity that DBMS provides. Some ensure correct data type, while others ensure legal values and formats.
Key integrity is an important function of DBMS that enables to enforcement of data integrity. It ensures that the primary key of a record remains unique and allows the record to be identified uniquely.
Major Components of Database Management
There are several components of DBMS that enable it to work smoothly.
The main components of DBMS are depicted in Figure :
A description of these components is as follows:
DMBS Engine
It is a core service for storing, processing, and securing data. It is an interface between a user and the physical database. DBMS Engine involves accepting queries/commands from different DBMS users and converting them, so the database can understand them.
DBMS Engine then interacts with the physical database to produce the result. It can access the database and the data dictionary because these are available in the storage device.
Data Definition Subsystem
This component of DBMS enables only authorized users to create and maintain the data dictionary and define the structure of the files in a database as to how the data will be stored in the database.
Data Manipulation Subsystem
This subsystem enables users to add, change, and delete data in a database and query it for decision-making processes in an organization. Various software tools are available within the data manipulation subsystem that is the primary interface between the user and the data contained in a database. Using these tools, a user can specify his/her logical data requirements, which can then be fulfilled by this subsystem.
Application Generation Subsystem
This subsystem contains facilities to enable users to develop transaction-intensive applications. Usually, a user is required to perform a detailed series of tasks to perform a transaction on a database. An application generation subsystem facilitates users to create such applications with easy-to-use data-entry screens, programming languages, and interfaces.
Data Administration Subsystem
This subsystem helps users manage the overall database environment by providing facilities for database backup and recovery, security management, query optimization (fast retrieval of data), concurrency control (simultaneous request for retrieval of data), and change management.
