Database Management System - Essay Example

22-02-2007 Database Management System Data and information are two basic components of any information system. Data is defined as a set of basic facts and entities which itself has no meaning or value. Data is considered the raw material of an information system. An information system transforms data into meaningful management information. Business processes, which are essence of the business, are always associated with a huge amount of data. The objective of an information system is to provide the required information to the organization, o that the business processes can be managed effectively. It is essential or the organization to develop an effective database system. Database is defines as a system, used to record and maintains data. The most important point to understand database is that database contains data and not necessarily information. The database is a collection of interrelated data, which can be used by one or more applications that it can be integrated and is stored in a shared and organized way so that it has a controlled redundancy, consistency and integrity with a provision of data independence. The database is used to store and process data for providing useful organization. The database must have the following basic objectives i.e., centrally controlled which facilitates data can be stored, processed, modified or accessed in a organized way. Database must be organized in such a way that the redundancy and inconsistency can be avoided as much as possible. Database must be centrally controlled so that its integrity, security and privacy can be maintained database must be logically organized, integrated, designed to multi used application and provision for data independence whether physical or logical. So a database system is a system, which defines, interprets, manipulates and maintains a collection of database, which is entirely separate in structure. Database management system (DBMS) is the major component of the database system. The DBMS is the foundation of almost every modern business information system. Database management system is defined as a system so software that organizes and maintains the data in a database for providing the information. A DBMS is a very complex piece of system software. A single DBMS can manage multiple databases each one usually consisting of many different tables full of data. The DBMS includes mechanism for application programs to store, retrieve and modify this data and also allows people to query it interactivity to answer specific questions. DBMS can be divided into four major components i.e. Database, Database administrator (DBA), Database users and database programs specialists known as DBA's control the operation of the DBMS and are responsible for the creation of new data bases and the definition of the table structures used to store data. One of the most important features of the DBMS is its ability to shield the people and programs using the data from the details of its physical storage. Because all access to stored data is mediated through the DBMS, a database can be restructured or moved to a different computer without disrupting the programs written to use it. The DBMS polices access to the stored data, giving access only to tables and records for which a given user has been authorized. The DBMS evolved from a more humble class of programs known as file management systems, created within the unglamorous world of corporate data processing to simplify the creation of programs for routine administration. The database management system conflated the managerial concept of the database with the specific technology of the file management system. In practice, the DBMS worked well as technical system to aid application programmers but disappointed as a managerial panacea (Haigh, 2006). The corporate database has originally been conceived as a repository of all-important managerial information; actual DBMS technology supported only the kind of highly structured regular records with which earlier file management systems had been adept. Advantages of a DBMS: The database management system is essential for computerized management. It is required to meet the objectives of database. The major objectives and advantages of a DBMS are summarized as follows: Provide the way for shortage of data and information (data definition), Provide centralized control and an easy access to the data, Provide the way for doing simple and complex queries on a database, Arranging the data in various way, Maintain non-redundancy of data, Maintain the integrity to ensure that the data is correct, Maintain security and privacy of data, Provide access to multiple users, Provide an integrated and shared system, Provide the method for data independence. Disadvantages of a DBMS: Costly due to requirements of expensive hardware and higher operating costs, Greater complexity of backup and recovery in multi-user environment, High risk of data loss due to centralization of database. During the 1970s, when data base management systems were first promoted to corporate managers, they were sold as the technological means by which all of a company's computerized information could be assimilated into a single integrated pool of data. Early, rather vague, concepts of data pools embedded the assumption that all relevant information, whether internal or external, past or future, economic or human, could be accommodated within a single structure. The 1950s had seen a sudden proliferation of discussion about information within a number of different fields. Shannon's mathematical theory of digital communication (Shannon and Weaver, 1949) was picked up as a powerful metaphor within the nascent meta-discipline of cybernetics. Librarians specializing in scientific and technical fields began to speak of themselves as information scientists (Wellisch, 1972), while researchers attempting to automate record searching started to call this work information retrieval (Bowles1999; Miller, 1961). Glowing reports in Fortune magazine informed businessmen of the power of information theory (Bello, 1953) and of information retrieval (Bello, 1960). In 1958, the combination of computers, operations research methods and simulation was first dubbed "information technology"(Leavitt and Whisler, 1958). Stone, who first introduced managers to the idea of information as a generalized, abstract entity, separate from the forms, reports, files and memos in which it had previously been embodied. Stone recognized that a flexible and complete MIS could only be constructed if a firm's entire mass of paperwork could be computerized and integrated "to produce an interrelated body of useful data, or information"(Stone, 1960, page 17). Another consultant suggested that the office of the future would revolve around a "data hub", defined as "a central source of information that can serve as an instant inquiry station for executives who need data for decisions" (Weindling, 1961). Representatives of Shell Oil spoke of the need for an "electronic data bank, or pool of information, from which reports of many types can be drawn" (Haslett, 1962; Keller, 1976). The other main intellectual ingredient of the Data Base Management System, and the key technological foundation for the actual data base management systems of the 1970s, was the "file management system" (together with its close relation, the "report generator"). File management systems were intended to reduce the cost of producing routine administrative programs, and to make the finished programs easier to change and maintain. Report generation systems made it easier to produce printed reports based on particular criteria. These ideas, unlike the data base concept itself, were indigenous to the world of administrative data processing, where they had slowly evolved. File management systems evolved from the reuse of subroutines written to handle input and output tasks within application programs. Early computer programs included all the instructions necessary to specify the minute details of reading and writing information from tape or disk, and were forced to check regularly whether a particular record had yet been retrieved (McCracken, Weiss and Lee, 1959, 178-204). File management systems also proved an important niche for the nascent independent software package industry. Data storage and retrieval are two important driving forces behind data management. There are many methods of organizing data. There are four common methods of organizing files: 1) Serial organization 2) Sequential organization 3) Random file organization 4) Indexed sequential organization. These file management techniques were very useful with tape storage, but when firms began to start storing their data on disk drives, the extra complexity of programming random access data storage and retrieval made their use almost essential. Disk drives, however, offered "random access" storage, giving almost instant access to any part of a disk. This promised to allow the speedy retrieval of specific data as needed, making it much easier to create special reports or to build on-line business systems such as the celebrated SABRE airline reservation system (Copeland, Mason and McKenney, 1995; Parker, 1965). Until about 1968, the concepts of databases and file management systems remained largely distinct. Combining the database and the file management system created the Data Base Management System. The DBMS was intended to be a new kind of product, extending the capabilities of existing file management systems to support the kind of advanced, on-line, interactive capabilities and huge integrated data stores associated with the data base concept. The DBMS was intended to make these relationships (or, as the DBTG called them, "sets") as explicit and enforceable as previous file management systems had made the specification of fields within an individual file. A database system can be designed in many ways. It is essential to understand the structure of data items as they relate to data users in an organization. This understanding of the data structures is represented as a data model. There are three classes of data models or schemas i.e. External schema (user view), conceptual schema (physical data model) and internal schema (physical data model). The major objective of a DBMS is to provide storage of data and information. The way of defining and storing data is known as data definition. To define data structure several types of languages are needed which can be categorized as Data description languages (DDL), Data Manipulation Language (DML) and Programming languages. At external or user level, there are three traditional ways of data representations (Data structures/models/schemas)- Hierarchical, Relational and Network structure. The relational model was far more conceptually elegant and flexible than the network model endorsed by CODASYL, which proved both restrictive (because relationships must be specified when the data base is designed) and insufficiently abstracted from the physical storage of data (programmers were still forced to write code to navigate explicitly from one record to another when working with linked data). Because the relational model shifted the responsibility of specifying relationships between tables from the person designing them to the person querying them, it permitted tables to be joined in different ways for different purposes. This turned out to be necessary (if not sufficient) for the establishment of large, general purposes databases shared between different departments and computer systems. The relational model has also been praised for its non-procedural nature - further separating the user from the physical storage mechanisms involved (Miller, 1961). Use of early DBMS systems was highly concentrated. The first widely used relational DBMS, Oracle, was launched in 1980 and found an early niche in the rapidly growing market for minicomputer systems. During the 1990s, relational systems gained the power and maturity to gradually edge out earlier mainframe products such as IMS, though even today the transition is far from complete. At the same time, the increasing power of personal computer systems opened new niches for DBMS technology on desktop computers and inexpensive departmental servers. Almost every custom business application produced during the past decade relies on a relational DBMS to store and retrieve data. Relational DBMS systems are widely used on personal computers. Indeed, Microsoft now bundles a version of its powerful SQL Server DBMS with the "professional" editions of its Office suite, and has even adapted it for use with its Pocket PC hand held computers. Microsoft has long aimed, though so far without success, to replace the conventional file system and the email repositories found on today's Windows operating systems with a multitalented DBMS. In some ways, the DBMS has indeed become a universal container for computer data. DBMSs based on the relational model continued to incorporate the same assumptions about information as earlier file management systems. In particular, the complexity of relational query construction meant that to query and update the database still required the involvement of a programmer, a specially written application program, or trained specialist. The designers of the now-standard SQL language had assumed that replacing algebraic characters with words such as "SELECT" would make it easy for managers to write their own queries but the complexity and rigor could not be removed so easily. And although the relational model made it easier to join tables together in different ways, data base designers still had to specify the exact format of each column within the table, and include exactly the same fields in each row. As DBMS use proliferated, firms found themselves unable to integrate all corporate data into a single pool in the manner promised by early data base advocates. When DBMS technology achieved almost universal use, large firms were left with hundreds or thousands of disconnected and duplicated databases and no easy way to merge them. Data warehousing, one of the leading obsessions of corporate IT departments and consulting firms of the mid- and late-1990s, was an attempt to construct enormous read-only data bases for reporting purposes in which all data was linked and reformatted into a standard form. Data pools imagined years ago have inched ever closer to reality, yet the messy reality of specialized, limited and inflexible data storage technologies continues to contrast with the pristine simplicity of the original vision. *************************************************************** References: 1. Bello, F. (September 1960), How to Cope with Information, Fortune, 62, 3, 162-167, 180-182, 187-189, 192. 2. Bello, F. (1953), The Information Theory Fortune, 136-141, 149-150, 152, 154,156, 158. 3. 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In American Management Association ed. Data Processing Today: A Progress Report -- New Concepts, Techniques and Applications -- AMA Management Report Number 46, American Management Association, Finance Division, New York, 14-22. 15. Weindling, R.E. (January 1961), Office Will Run Every Business Activity, Office Management and American Business, 22, 1 12-15. 16. Wellisch, H. (July 1972), From Information Science to Informatics: A Terminological Investigation, Journal of Librarianship, 4, 3, 157-187. Read More