INTRODUCTION TO DATABASE-MANAGEMENT SYSTEM

Database Management System:

•  A database-management system (DBMS) is a collection of interrelated data and a set of programs to access those data. 
• The DBMS is a general purpose software system that facilitates the process of defining constructing and manipulating databases for various applications.

 Goals of DBMS:

 The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient
1.Manage large bodies of information 
2. Provide convenient and efficient ways to store and access information 
3. Secure information against system failure or tampering 
4. Permit data to be shared among multiple users

Properties of DBMS:

•  1.A Database represents some aspect of the real world. Changes to the real world reflected in the database. 
• 2.A Database is a logically coherent collection of data with some inherent meaning. 
• 3.A Database is designed and populated with data for a specific purpose. 

Need of DBMS:

•  1. Before the advent of DBMS, organizations typically stored information using a “File Processing Systems”. Example of such systems is File Handling in High Level Languages like C, Basic and COBOL etc., these systems have Major disadvantages to perform the Data Manipulation. So to overcome those drawbacks now we are using the DBMS. 
• 2.Database systems are designed to manage large bodies of information. 
• 3. In addition to that the database system must ensure the safety of the information stored, despite system crashes or attempts at unauthorized access. If data are to be shared among several users, the system must avoid possible anomalous results.

 ADVANTAGES OF A DBMS OVER FILE SYSTEM:

 Using a DBMS to manage data has many advantages:

 Data Independence:

 Application programs should be as independent as possible from details of data representation and storage. The DBMS can provide an abstract view of the data to insulate application code from such details. Efficient Data Access: A DBMS utilizes a variety of sophisticated techniques to store and retrieve data efficiently. This feature is especially important if the data is stored on external storage devices.

Data Integrity and Security:

 If data is always accessed through the DBMS, the DBMS can enforce integrity constraints on the data. For example, before inserting salary information for an employee, the DBMS can check that the department budget is not exceeded. Also, the DBMS can enforce access controls that govern what data is visible to different classes of users

 Concurrent Access and Crash Recovery: 

A database system allows several users to access the database concurrently. Answering different questions from different users with the same (base) data is a central aspect of an information system. Such concurrent use of data increases the economy of a system. An example for concurrent use is the travel database of a bigger travel agency. The employees of different branches can access the database concurrently and book journeys for their clients. Each travel agent sees on his interface if there are still seats available for a specific journey or if it is already fully booked. A DBMS also protects data from failures such as power failures and crashes etc. by the recovery schemes such as backup mechanisms and log files etc.

Data Administration: 

When several users share the data, centralizing the administration of data can offer significant improvements. Experienced professionals, who understand the nature of the data being managed, and how different groups of users use it, can be responsible for organizing the data representation to minimize redundancy and fine-tuning the storage of the data to make retrieval efficient.

Reduced Application Development Time:

 DBMS supports many important functions that are common to many applications accessing data stored in the DBMS. This, in conjunction with the high-level interface to the data, facilitates quick development of applications. Such applications are also likely to be more robust than applications developed from scratch because many important tasks are handled by the DBMS instead of being implemented by the application.

DISADVANTAGES OF DBMS:

 Danger of a Overkill:

 For small and simple applications for single users a database system is often not advisable. Complexity: A database system creates additional complexity and requirements. The supply and operation of a database management system with several users and databases is quite costly and demanding.

 Qualified Personnel:

 `The professional operation of a database system requires appropriately trained staff. Without a qualified database administrator nothing will work for long.

Costs:

 Through the use of a database system new costs are generated for the system itself but also for additional hardware and the more complex handling of the system.

Lower Efficiency:

 A database system is a multi-use software which is often less efficient than specialized software which is produced and optimized exactly for one problem