Introduction And Overview Of Database Management Systems Computer Science Essay

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A database is a collection of information that is organized so that it can easily be accessed, managed, and updated. Databases can be classified according to types of content: bibliographic, full-text, numeric, and images. A database consists of an organized collection of data for one or more uses, typically in digital form. Digital databases are managed using database management systems, which store database contents, allowing data creation and maintenance, and search and other access.

In computing, databases are sometimes classified according to their organizational approach. The most prevalent approach is the relational database, a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. A distributed database is one that can be dispersed or replicated among different points in a network. An object-oriented programming database is one that is congruent with the data defined in object classes and subclasses.

Database Management Systems(DBMS)

A Database Management System (DBMS) is a set of computer programs that controls the creation, maintenance, and the use of a database. DBMS is a system software package that helps the use of integrated collection of data records and files known as databases. It is also the systematic approach of creating, maintaining, accessing, reporting, and analyzing attribute (alphanumeric or text) data and it is a software used to manage a database, i.e. allowing insertion of new data, update or deletion of old data, and retrieval of stored data by imposing constraints. DBMSs are categorized according to their data structures or types. The DBMS accepts requests for data from an application program and instructs the operating system to transfer the appropriate data. The queries and responses must be submitted and received according to a format that conforms to one or more applicable protocols. DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standard operating system to provide these functions.

In short, a collection of interrelated data together with a set of programs to access the data, also called database system, or simply database. The primary goal of such a system is to provide an environment that is both convenient and efficient to use in retrieving and storing information

History of Database Management Systems

Databases have been in use since the earliest days of electronic computing. Originally DBMSs were found only in large organizations with the computer hardware needed to support large data sets.

Navigational DBMS

A number of general-purpose database systems emerged by the mid-1960s which were of commercial use. Charles Bachman, author of the product, Integrated Data Store (IDS), founded the "Database Task Group" within CODASYL (Conference on Data System Languages) , the group responsible for the creation and standardization of COBOL.

The Codasyl approach was based on the "manual" navigation of a linked data set which was formed into a large network. When the database was first opened, the program was handed back a link to the first record in the database, which also contained pointers to other pieces of data.. IBM also had their own DBMS system in 1968, known as IMS. IMS was a development of software written for the Apollo program on the System/360. IMS was generally similar in concept to Codasyl, but used a strict hierarchy for its model of data navigation instead of Codasyl's network model. Both concepts later became know Later IMS was classified as a hierarchical database. IMS and IDMS, both CODASYL databases, as well as CINCOMs TOTAL database were classified as network databasesn as navigational databases due to the way data was accessed.

Limitation

The limitations of codasyl approach was that the programmer had to step through these pointers one at a time until the required record was returned to find any particular record. There was, essentially, no concept of "find" or "search" which is a serious limitation today.

Relational DBMS

Edgar Codd worked at IBM in San Jose, California, in one of their offshoot offices that was primarily involved in the development of hard disk systems. In 1970, he wrote a number of papers that outlined a new approach to database construction. In this paper, he described a new system for storing and working with large databases. Instead of records being stored in some sort of linked list of free-form records as in Codasyl, Codd's idea was to use a "table" of fixed-length records. A linked-list system would be very inefficient when storing "sparse" databases where some of the data for any one record could be left empty. The relational model solved this by splitting the data into a series of normalized tables, with optional elements being moved out of the main table to where they would take up room only if needed.

Linking the information back together is the key to this system. In the relational model, some bit of information was used as a "key", uniquely defining a particular record. When information was being collected about a user, information stored in the optional (or related) tables would be found by searching for this key. For instance, if the login name of a user is unique, addresses and phone numbers for that user would be recorded with the login name as its key. This "re-linking" of related data back into a single collection is something that traditional computer languages are not designed for.

Just as the navigational approach would require programs to loop in order to collect records, the relational approach would require loops to collect information about any one record.Using a branch of mathematics known as tuple calculus, he demonstrated that such a system could support all the operations of normal databases (inserting, updating etc.) as well as providing a simple system for finding and returning sets of data in a single operation.

SQL DBMS

IBM started working on a prototype system loosely based on Codd's concepts as System R in the early 1970s. The first version was ready in 1974/5, and work then started on multi-table systems in which the data could be split so that all of the data for a record (much of which is often optional) did not have to be stored in a single large "chunk". Subsequent multi-user versions were tested by customers in 1978 and 1979, by which time a standardized query language, SQL, had been added. Codd's ideas were establishing themselves as both workable and superior to Codasyl, pushing IBM to develop a true production version of System R, known as SQL/DS, and, later, Database 2 (DB2).

Object Oriented Database

The 1980s, along with a rise in object oriented programming, saw a growth in how data in various databases were handled. Programmers and designers began to treat the data in their databases as objects.

In 1989, two professors from the University of Michigan at Madison, published an article at an ACM associated conference outlining their methods on increasing database performance. This meant that a query could search the smaller database much quicker, rather than search the entire dataset.]This eventually leads to the practice of indexing, which is used by almost every operating system from Windows to the system that operates Apple iPod devices

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