Managing data Resources: An information system provides users with timely, accurate, and relevant information. The information is stored in computer files. When files are properly arranged and maintained, users can easily access and retrieve the information when they need. If the files are not properly managed, they can lead to chaos in information processing. Even if the hardware and software are excellent, the information system can be very inefficient because of poor file management.

File Organization Terms and Concepts A computer system organizes data in a hierarchy that starts with the bit. Bit represents 0 or 1. 8 bits are grouped to form a byte. Each byte represents one character, number , or symbol. Bytes can be grouped to form a field. It can represents a person’s name or age. Related fields can be grouped to form a record. Related fields can be student’s name, course taken and the grade. Related records can be grouped to form a file. Related files can be grouped to form a database

The Data Hierarchy Course File Financial File Database Student database Personal History File Cynthia Lokker CIS 500 A Daniel Boles IST 203 B File attribute NAME COURSE GRADE Record Cynthia Lokker CIS 500 A Field Cynthia Lokker (NAME field) Byte 01000001 (letter A in ASCII) 0 or 1 Bit

More File Organization Terms Key field Every record in a file should contain at least one field that uniquely identifies that record so that the record can be retrieved, updated, or sorted. This identifier field is called a key field. Cynthia Lokker 959010054 CIS 500 A Daniel Boles 969010055 IST 203 B NAME STUDENT # COURSE GRADE Key field Entity A person, place, thing, or event on which we maintain information.

Accessing Records from Computer Files Computer stores files on secondary storage devices. Records can be arranged in several ways on storage media. How individual record scan be accessed or retrieved depends on how they are arranged on storage media. There are mainly two ways to organize records: sequentially or randomly. In sequential file organization, data records must be retrieved in the same physical sequence in which they are stored. In direct or random file organization, data records can be accessed in any sequence as users desire, without regard to actual physical order on the storage media. Sequential file organization is the only file organization that can be used on magnetic tape. Example: Payroll Direct or random file organization is utilized with magnetic disk. Most computer applications utilize this method.

Problems of the Traditional File Environment Data redundancy is the presence of duplicate data in multiple data files. In this situation confusion results because the data can have different meanings in different files. Program-data dependence is the tight relationship between data stored in files and the specific programs required to update and maintain those files. This dependency is very inefficient, resulting in the need to make changes in many programs when a common piece of data (such as zip code) changes. Lack of flexibility refers to the fact that it is very difficult to create new reports from the data when needed. Ad hoc reports are impossible; a new report could require several weeks of work by more than one programmer and the creation of intermediate files to combine data from disparate files. Poor security is a problem resulting from the lack of control over the data because it is widespread and distributed into so many files.

Database and Database Management System Database => A database is a collection of data organized to service many applications efficiently by centralizing the data and minimizing redundant data. Database management System => A database management system is a special software that permits an organization to centralize data, manage it efficiently, and provide access to the stored data by application programs.

The Components of a DBMS The data definition language which is the formal language used by programmer to specify the content and structure of the database. The data manipulation language, which is used to manipulate the data in database. The data dictionary, which is an automated or manual file that stores definitions of data elements and data characteristics such as usage, physical representation, ownership and security.

Logical and Physical View of Data A logical view of data is the way data is perceived by end users or business specialists. A physical view of data is the way the data are actually organized and structured on physical storage media.

Advantages of a DBMS Complexity of the information system environment can be reduced. Data redundancy and inconsistency can be reduced. Data confusion can be eliminated. Program-data dependency can be reduced. Program development and maintenance costs can be reduced. Flexibility of IS can be enhanced. Access and availability of information system can be increased.

Normalization Normalization is used to streamline the database design by removing redundant data, such as repeating groups. A database that is not normalized will have inefficient queries and will delete information when it should not or update only part of the information.

Distributed Database A distributed database is partitioned, or distributed among more than one physical locations. Parts of the database are stored in one location and other parts are stored and maintained in other locations. One main central database can be partitioned into multiple local databases. These databases can be updated locally and later justified with the central database. Alternately, the central database can be duplicated at various remote locations. Another possibility is to maintain a central index and have complete records stored at local levels

Successful Database Environment Data administration=> the policies, procedures, and tools for managing and planning for information as a corporate source. A data planning and modeling methodology from an enterprise-wide perspective. Users=> end users have a wide role with DBMS than in traditional systems and they must be trained. Database technology and management=> DBMS software maintained by firm’s database administration group.