Introduction to Databases

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Part 1 Background

Chapter 1 Introduction to Databases

1.1A database management system provides a number of facilities that will vary from system to system. Describe the type of facilities you might expect, especially those that aid the initial implementation of a database and its subsequent administration.

Initially, the type of facilities expected should be described. These include: data storage and retrieval, concurrency control mechanism, authorization services, integrity mechanisms and transaction support. The focus is then on facilities such as data definition, which is stored in the catalog, authorization control to manage the users. View definition, transaction support and integrity controls also aid subsequent administration.

1.2Discuss the problems that arise when organizations rely upon multiple computerized file systems to store data.

Discuss the advantages and disadvantages in using a database management system to carry out the same functions.

For the first part the answer should cover broadly all the problems associated with file-based systems, such as: data duplication, data inconsistency, problems with validation and security, fragmentation of data.

For the second part, the focus is on a DBMS to support the same operations. Advantages include: providing all the data structuring facilities, security mechanisms, integrity mechanisms, backup and recovery facilities, minimal redundancy, data sharing, data independence. Disadvantages include: cost, size, complexity.

1.3Applications built around file management systems have often been used to satisfy user requirements. Discuss the problems that arise with such systems, and what advantages a database management system could offer instead.

This answer contains the points made in part one of the previous question and also includes the advantages contained in part two of the previous question.

1.4Explain what is meant by a database management system, and contrast it with a File Management System.

Give a full account of the type of system structure you might expect for a Database Management System, and outline the type of facilities such a system should provide.

If you were in the position of appraising an application for possible implementation using a Database Management System, what aspects of the application would you consider with respect to the advice you might give?

First part: For a DBMS, the emphasis is on the management of a collection of data as a resource that is accessible to different users for different purposes. In contrast, a File Management System (FMS) manages a collection of files for a specific purpose. Different FMSs have their own collection of files and cannot share data. Additional details should focus on aspects such as data redundancy, data sharing, data independence.

Second part: A diagram illustrating typical system structure would be useful. It should show the DBMS as a suite of programs/modules, each with specific functions. Following on from this, the typical facilities provided can be described.

Third part: Perhaps consider: how many users there are requiring different data, the type of application it is (such as, interactive with many screens), is it part of a larger set of applications, is it likely to be extended in the future, are the data relationships complex, are various integrity controls needed.

Chapter 2 Database Environment

2.1Discuss the reasons for the three-level architecture for a Database Management System.

A diagram would be useful to illustrate the relationships between the external, conceptual, and internal levels. The different levels should be explained, and reference should be made to the need for logical and physical data independence. This should be explained also using examples.

2.2Security and recovery are two important functions of a Database Management System, which are also of interest to Database Administration. Various facilities...
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