Chapter 8 Managing Data Resources. Chapter 82 Managing Data Resources 8.1 Organizing Data in a Traditional File Environment –An effective information

Chapter 8

Managing Data Resources

Chapter 82


• 8.1 Organizing Data in a Traditional File Environment– An effective information system provides users with

timely, accurate, and relevant information. – When the files are properly arranged and maintained,

users can easily access and retrieve the information.– Well-managed, carefully arranged files make it easy to

obtain data for business decisions.– 8.1.1 File Organization Terms and Concepts:

• A computer system organizes data in a hierarchy that starts with bits and bytes and progresses to fields, records, files, and databases.

Chapter 83


• A group of bits, called byte, represents a single character, which can be letter, a number, or another symbol.

• A grouping of characters into a word, a group of words, or a complete number, is called field.

• A group of fields comprises a record.• A group of records of the same type is called a file.• A record describes an entity. An entity is a person,

place, thing, or event on which we maintain info.• Each characteristic or quality describing a particular

entity is called an attribute.

Chapter 84


• Every record in a file should contain at least one field that uniquely identifies that record, which is called key field.

– 8.1.2 Accessing Records from Computer Files• Sequential file organization, data records must be retrieved in

the same physical sequence in which they are stored

• Direct/random file organization allows users to access records in any sequence they desire.

• Transform algorithm is a mathematical formula to translate the key field directly into the record’s physical storage location on disk.

Chapter 85


– 8.1.3 Problems with the Traditional File Environment

• Each functional area tended to develop systems in isolation from other functional areas.

• The isolated systems lead to hundreds of programs and applications.

• These systems result in data redundancy, program-data dependence, inflexibility, poor data security, and inability to share data among applications.

• Data redundancy and confusion is the presence of duplicate data in multiple data files.

Chapter 86


• Program-data dependence is the tight relationship between data stored in files and the specific programs required to update and maintain those files.

• Lack of flexibility means the inability to deliver ad hoc reports or respond to unanticipated information requirements in a timely fashion.

• Poor security for the data because of little control or management of data, access to and dissemination of information are virtually out of control.

• Lack of data-sharing and availability means it is hard for people to obtain information as a result of the scattered pieces of data among different files and different parts of the org.

Chapter 87


• 8.2 The Database Environment– Database is a collection of data organized to serve

many applications efficiently by centralizing the data and minimizing redundant data.

– 8.2.1 Database Management Systems• It is simply the software that permits an organization to

centralize data, manage them efficiently, and provide access to the stored data by application programs.

• It acts as an interface between application programs and the physical data files.

• Three elements of database management system:

Chapter 88


• Data definition language is the formal language used by programmers to specify the content and structure of the database.

• Data manipulation language is the language used with other conventional third- or fourth-generation lang. to manipulate the data in the database and extract the needed data from it.

• Structured Query Language (SQL) is the most prominent data manipulation lang.

• Data dictionary is an automated or manual tool for storing and organizing information about the data maintained in a database.

• Data element represents a field.• Logical view presents data from end user’s perspective.• Physical view shows how data are actually organized physically.

Chapter 89


• 8.3 Designing Databases– 8.3.1 Hierarchical Data Model

• The hierarchical data model presents data to users in a treelike structure. Within each record, data elements are organized into pieces of records called segments.

• Behind the logical view of data are a number of pointers, which physically link the data items one to another.

– 8.3.2 Network Data Model• The network data model is a variation of the hierarchical data

model. • The databases can be translated from hierarchical to network

and vice versa to optimize processing speed and convenience.

Chapter 810


• Whereas the hierarchical depict one-to-many relationships, network model depicts as many-to-many relationships.

• Each parent can have multiple children, and a child can have more than one parent.

– 8.3.3 Relational Data Model• The relational data model represents all data in the database

as simple two-dimensional tables called relations. • Often a user needs information from a number of relations to

produce a report.• It can relate data in any one file or table to data in another file

or table as long as both tables share a common data element.• Three basic operations are used to develop useful sets of data:

select, project, and join.

Chapter 811


• Select creates a subset consisting of all records that meet a condition criteria.

• Join operation combines tables to provide the user with more information than is available in one table.

• Project operation creates a subset consisting of columns in a table.

– 8.3.4 Advantages and Disadvantages of the Three Database Models

• The advantage of network and hierarchical is processing efficiency.

• Their disadvantage is that all the access paths, directories, and indices must be specified in advance.

Chapter 812


• Moreover, they are both programming intensive and time consuming, difficult to install, and difficult to remedy.

• The strengths of relational DBMS are:– great flexibility in regard to ad hoc queries, – power to combine info from different sources, – simplicity of design and maintenance, and – ability to add new data and records.

• However, these systems are somewhat slower because they typically require many accesses to the data stored on disk.

Chapter 813


– 8.3.5 Creating a Database• Two design phases are required: conceptual and physical

designs.• The physical design shows how the database is actually arranged

on direct access storage devices.• Conceptual design describes how the data elements in the

database are to be grouped.• It identifies the relationships among data elements and the most

efficient way of grouping data elements together to meet information requirements.

• Entity-relationship diagram is a methodology for documenting databases illustrating the relationship between various entities in the database.

• Normalization is to create the small stable data structures.

Chapter 814


Student Registered in

Course

Taught byInstructor

M M

M

1

Chapter 815


• 8.4 Database Trends– 8.4.1 Distributed Databases

• A distributed database is one that is stored in more than one physical location.

• Parts of the database are stored physically in one location, and other parts are stored and maintained in other locations.

• Two main ways of distributing a database.

• The central database can be partitioned so that each remote processor has the necessary data to serve its local area.

• Another strategy is to replicate the central database at all remote locations.

Chapter 816


• Both distributed processing and distributed databases have benefits and drawbacks.

• Distributed systems reduce the vulnerability of a single, massive central site, permit increases in systems’ power by purchasing smaller, less expensive computers, and increase service and responsiveness to local users.

• However, they are dependent on high-quality telecommunications lines, they can sometimes depart from central data standards and definitions, pose security problems, and the economies of distribution can be lost when remote site buy more computing power.

Chapter 817


– 8.4.2 Object-Oriented and Hypermedia Databases• The new applications require databases that can store and

retrieve drawings, photographs, voice, and full-motion video.• Object-oriented database stores data and procedures as

objects that can be automatically retrieved and shared.• The hypermedia database approach transcends some of the

limitations of traditional database by storing chunks of info in the form of nodes connected by links established by the user.

• The relationship between records is less structured.

– 8.4.3 Multidimensional Data Analysis• Some data analysis cannot be represented by traditional ways.• Multidimensional analysis enables users to view the same data

in different ways using multiple dimensions.

Chapter 818


– 8.4.4 Data Warehouses• Data warehouse is to integrate key operational data from

around the company in a form that is consistent, reliable, and easily available for reporting.

• It is a database, with tools, that stores current and historical data of potential interest to managers throughout the company.

• The data are available but cannot be altered.

• It includes a range of ad hoc and standardized query tools, analytical tools, and graphical reporting facilities.

Chapter 819


• 8.5 Management Requirements for Database Systems– Much more is required for the development of database

systems than simply selecting a logical database model.– 8.5.1 Data Administration

• Database systems require that the organization recognize the strategic role of information and begin actively to manage and plan for information as a corporate resource.

• Data admin is responsible for the specific policies and procedures through which data can be managed as an organizational resource (developing info policy, planning for data, overseeing logical database design and data dictionary development, and monitoring the data usage).

Chapter 820


• An organization needs to formulate an information policy that specifies its rules for sharing, disseminating, acquiring, standardizing, classifying, and inventorying information throughout the org.

– 8.5.2 Data Planning and Modeling Methodology• The org. requires enterprise-wide planning for data.• The purpose of enterprise analysis is to identify the key

identities, attributes, and relationships that constitute the org. data.

– 8.5.3 Database Technology, Management, and Users• Databases require new software, new trained staff, and new

management structures.

Chapter 821


• The IS division is responsible for the technical and operational aspects of managing data., which called database admin that do the following:

1. Defines and organizes database structure and content

2. Develops security procedures

3. Develops database documentation

4. Maintains the database mgmt software

• The IS division is responsible for the technical and operational aspects of managing data., which called database admin that do the following:

1. Defines and organizes database structure and content

2. Develops security procedures

3. Develops database documentation

4. Maintains the database mgmt software

Managing Data ResourcesManaging Data Resources

Documents

Chapter 8 Managing Data Resources. Chapter 82 Managing Data Resources 8.1 Organizing Data in a Traditional File Environment –An effective information