Introduction to DBMS

Database Management Systems – Purpose

Today, Knowledge about database systems is an integral part of education in every field.

A database is a collection of data typically describes the activities pertaining either within the organization or across related organizations.  

A DBMS is software designed to assist in maintaining and utilizing large collections of data. Databases are so widely used today and can be found in organizations of all sizes ranging from large environment agencies   to small businesses and homes.  Everyday activities bring all of us to contact with databases.

We all know that databases are used in different walks of life.  Databases make life much simpler. Railway reservations, hotel reservations, student records in a university are examples with which all of us are familiar. We do not have to stand in long queues and the reservations clerk does not have to fiddle with many files and fill up forms. Different organizations of the governments use databases in a big way. Tax records, crime records, passports, etc. are examples for this kind. All big corporate houses use databases in their day-to-day functioning in HRD, accounts, sales, etc.

When we used credit card the sales person usually waits for computer approval of your purchase before you sign your receipt. This approval process involves consulting a database to verify that your card has been not stolen or lost and to find your card limit, content balance and amount of purchases already approved. The database automatically updated to reflect the new approved amount. Similarly if you visit a doctor you may find that your medical records and billing data have been entered into the database.  If you have prescription filled, your pharmacist may use a database to record data about the prescription check for interactions with drugs you are using currently and print the label and receipt.  Both the doctor and pharmacist may use their databases to do third party billing for you, automatically generating insurance claims for covering expenditures.

Therefore, databases are used satisfy the information needs of many organizations and individuals in a variety of areas. However, a poorly designed database may fail to provide the required information or may provide outdated, flawed, or contradictory information. To maximize the potential benefits, it is important to understand the theoretical foundations internal structure, design, and management of databases. 

If you observe the applications discussed, information is important and hence we need set of concepts and techniques for managing data.

File Systems (late 1960s): As you can see the field of Data Collection and Database Creation begins with file systems during 1960’s. Typical Applications include Pay rolls, Utility bills and Tenth class   examination results of Andhra Pradesh. All of these applications have some Common Characteristics, they are

Batch requirements: That entire means is we have data, which is generated over an interval and based on that you prepare some reports like payrolls. So, you have set of employees and then every month you generate their pay slips, etc.

 Now these applications without responding to any query, it only generates some reports. These reports are rigid formatted and they have one user and one application. They are generally developed in COBOL.

In a typical file system, each department has its own set of applications and its own files. The file is designed specifically for these applications. Also some times the department specifically working with the data processing staff sets policies or standards for the format and maintenance of its files.  For example, in a college environment the admissions office may have programs to keep track of potential students and to generate letters and reports concerning their applications. The admission office decides what information is to be stored what data may be left blank in record, what abbreviations are to be used, how long records are to be maintained and under what situations file is to be updated. Since the department owns the file, this office also controls the access to the information. 

The figure shown on the slide depicts example for the traditional file processing system. In this diagram the accepted student data file, owned by the admissions office is used in a matriculation program to generate a list of matriculated students.  The matriculated students’ data file contains the information about the all active matriculated students. The Course Data file has information about the courses. These two files owned by registrar’s  office along with a temporary file  students ‘s course enrollment requests are used by scheduling program to produce  individual student schedules and class lists. The dean’s office may have its own files for student and course data as well as Deans faculty data file used to assign a final teaching schedule to each faculty. The faculty payroll data file has information needed for calculating pay and producing pay slips  and other pay roll reports. Each program contains details of the physical structure and storage of the file its accesses.

Consider the amount of duplication of labor and storage that these separate files represent. We noted that the records of accepted students may have to be re entered when they matriculate. In the process, new errors may be introduced.  The course data file includes some faculty information which is again repeated in the Dean’s faculty data file. In addition to wasting data entry time and storage space, this duplication leads to data inconsistency since an update such as a change of address may be performed on one file and may not be done in another file. Also when data is isolated in separate files, it is difficult to access information  that should be available.

 Integrated Database Environment:

Use of DBMS will help to overcome the problems of File-processing systems. File system is unsatisfactory because of DATA DEPENDENCE.    Change in requirement may force to change in representation.  Such changes may also indirectly change in programs as well.  Other reasons for using DBMS are Data isolation -   Data scattered in various files in various formats and difficult to write programs, Data redundancy & inconsistency:    Due to storage of data at multiple places. In the presence of updates, these lead to Inconsistency.

Compared to File base approach, the integrated database environment has a single large repository of data called database which is used simultaneously by many departments and users. Instead of disconnected files with redundant data, all data is stored together with minimum amount of repetition. Several different types of records may appear in the database along with logical connections among the data items and records.  The database is not owned by a single department but is shared resource. It is managed by an individual or group called the DBA. DBS is responsible for designing, creating and maintaining the database to satisfy the needs of users.

All access to the database is controlled by a sophisticated software package called DBMS. IT has programs to set up the storage structures load the data, accept data requests from programs and users format the retrieved data, hide the data allow concurrent use of data without having users to interfere  with each other and perform backup and recovery procedures automatically.

The following figure shows how the integrated database environment will support the drawbacks of file system approach.

Advantages of DBMS:  Various advantages of using DBMS are sharing of data, control of redundancy,    Data consistency,    Improved data standards, Better data security,    Improved data integrity, More control over concurrency, Better backup and recovery procedures,   Balancing conflicting requirements and   Better data accessibility.

Disadvantages of DBMS: Various disadvantages of DBMS are High cost of DBMS, Higher hardware costs, higher programming costs, Slower processing of some applications and Increased vulnerability.