Database Database is a large collection of related data that can be stored, generally describes activities of an organization. An organised collection of logically related data.

Purpose of DBMS The purpose of a database is to keep track of things Unlike a list or spreadsheet, a database may store information that is more complicated than a simple list Use a DBMS software to create, store, organize, and retrieve data from a single database or several databases Example: Microsoft Access

Characteristics of DBMS Data Independence Data Integrity Flexibility The database can grow, change and built up ,stage by stage. Self describing nature of database system Supports multiple views of data. Sharing of data , multiuser transaction processing Locking feature while updating a record.

security of files Allowed to have variable length record and should save space. It is computerised record keeping system Allows to modify the contents of file as well as addition and deletion of file. DBMS may contain many databases which can be used for separate or combined. It reduces data redundancy Operating environment independence means capability to run on many computers with certain types of OS. DBMS allows complex relationship between data files.

Data Independence Upper levels are unaffected by changes in lower level Changes in storage mechanism should not change application program Ability to modify structure at physical level without affecting structure at view level There are two kinds of independence: Physical- It indicates the physical storage structure or devices could be changed without affecting the conceptual schema. Logical- conceptual schema can be changed without affecting the existing external schema. It requires flexibility in the design of database and the programmer has to look forward and find requirements and modifications in the design.

Differences in data Independence Physical data Independence Logical data Independence It is the ability to modify the physical schema without causing application program to be rewritten. Modifications at physical level are necessary to improve performance. It is not difficult to achieve. The conceptual schema insulates the users from changes in physical storage of data. It is the ability to modify the logical schema without causing application program to be rewritten Modifications at logical level are necessary whenever the logical structure of the database is altered. It is more difficult to achieve as application programs are dependent on the logical structure of the data that they access. The users are shielded from changes in the logical structure of the data or changes in the choice of relation to be stored.

Purpose of DBMS To store data TO organise the data To control access to data To protect data

Uses of DBMS To provide decision support Managers and analysts retrieve generated by the DBMS for inquiry, analysis and decision making To provide transaction processing Users input , update, and process the data with transactions that generate information needed by managers and other users.