Types of DBMS

There are three main types of Database Management System (DBMS) and these types are based upon their management of database structures. In other words, the types of DBMS are entirely dependent upon how the database is structured by that particular DBMS. The types of DBMS are:

a) Hierarchical DBMS: A DBMS is said to be hierarchical if the relationships among data in the database are established in such a way that one data item is present as the subordinate of another one. Here subordinate means that items have 'parent-child' relationships among them. Direct relationships exist between any two records that are stored consecutively. The data structure "tree" is followed by the DBMS to structure the database. No backward movement is possible/allowed in the hierarchical database. Most of the older DBMS such as Dbase, FoxPro etc. are hierarchical which are rarely used now a days.

b) Network DBMS: A DBMS is said to be a Network DBMS if the relationships among data in the database are of type many-to-many. The relationships among many-to-many appears in the form of a network. Thus the structure of a network database is extremely complicated because of these many-to-many relationships in which one record can be used as a key of the entire database. A network database is structured in the form of a graph that is also a data structure. Though the structure of such a DBMS is highly complicated however it has two basic elements i.e. records and sets to designate many-to-many relationships. Mainly high-level languages such as Pascal, COBOL and FORTRAN etc. were used to implement the records and set structures.

c) Relational DBMS: A DBMS is said to be a Relational DBMS or RDBMS if the database relationships are treated in the form of a table. A statical table that is composed of rows and columns is used to organize the database and its structure and is actually a two dimension array in the computer memory. A number of RDBMS are available however the most popular are Oracle, Sybase, Ingress, Informix, Microsoft SQL Server, Microsoft Access and so on.

d) Object Oriented DBMS: Object Oriented Databases generally provide persistent storage for objects.  In addition, they may provide one or more of the following: a query language; indexing; transaction support with rollback and commit; the possibility of distributing objects transparently over many servers.  These features are described in the following sections.  Some database vendors may charge separately for some of these features.

Some Object Oriented Databases also come with extra tools such as visual schema designers, Integrated Development Environments and debuggers.