Database Design Concepts
Introduction
The overall assignment deals with characteristics of database system, its approach and how it replaced the file based approach.
In every organization there is need of database. Database is collection of data in a structured and more systematic way that helps in retrieving the data easily and efficiently. Before database system came in to picture there was file based approach in which there were application programs which were used to perform services for end user and produce reports. However every program used to manage its own data. Due to this and various other limitations file system was replaced by database system.
The modern database approach has much advantage that helps not only the organization but also the common people in their day today life.
In the below assignment all the characteristics of database has been described.
Task 1: Describe the main characteristics of the database approach and contrast it with the file-based approach. Analyze the key issues and application of databases within organizational environments.
Main Characteristics of the Database Approach
Self-describing nature of a database system: A DBMS catalog stores the description of the database. The description is called meta-data which is data about data. This allows the DBMS software to work with different databases.
Insulation between programs and data: Also known as program-data independence. Without making any change to DBMS access programs the data storage structures and operations can be changed.
Data Abstraction: The availability of data model approach helps in hiding the physical view of data i.e. the storage details and other internal level information and provides the conceptual view of database.
Support of multiple views of the data: The database approach allows each user to have their own view of the database which describes only the data of interest to that user. There are various benefits of having multiple views such as:
Reduce complexity
Provide a level of security
Provide a mechanism to customize the appearance of the database
Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed
Sharing of data and multi-user transaction processing: The database approach allows a set of concurrent users to retrieve and to update the database. Spreadsheets cannot offer several users the ability to view and work on the different data in the same file, because once the first user opens the file it is locked to other users. Other users can read the file, but may not edit data. For example, when one user is changing data then the database should not allow other users who query the same data to view the changed, unsaved data. Instead the user should only view the original data.
Controlled access to database may include:
a security system
an integrity system
a concurrency control system
a recovery control system
a user-accessible catalog.
File-based System
File-based systems were the manual based approached used for managing the files. It’s mainly the collection of application programs that used to provide services for the end-users. Each program was defined for a specific task and can’t be used simultaneously with each other.
However, there are many pitfalls of file based system.
Separation and isolation of data
When data is isolated in separate files, it is more difficult for us to access data that should be available. The application programmer is required to synchronize the processing of two or more files to ensure the correct data is extracted.
Duplication of data
With the use of the decentralized file-based approach, the uncontrolled duplication of data used to occur which can lead to loss of data integrity as well as is wasteful as it occupies unnecessary space in memory storage area.
Data dependence
Using file-based system, the physical structure and storage of the data files and records are defined in the application program code. This makes the file to be program-data dependent. If the user want to make any change in the existing structure it was a difficult a task and will lead to a modification of program. Such maintenance activities are time-consuming and subject to error.
Incompatible file formats
The structures of the file are dependent on the application programming language. However file structure provided in one programming language such as direct file, indexed-sequential file which is available in COBOL programming, may be different from the structure generated by other programming language such as C. The direct incompatibility makes them difficult to process jointly.
Fixed queries / proliferation of application programs
File-based systems are very dependent upon the application programmer. Any required queries or reports have to be written by the application programmer. Normally, a fixed format query or report can only be entertained and no facility for ad-hoc queries if offered.
Database Approach:
In order to overcome the limitations of the file-based approach, the concept of database and the Database Management System (DMS) was emerged in 60s.
Advantages of DBMSs
Control of data redundancy
Data consistency
More information from the same amount of data
Sharing of data
Improved data integrity
Improved security
Enforcement of standards
Economy of scale
Balance conflicting requirements
Improved data accessibility and responsiveness
Increased productivity
Improved maintenance through data independence
Increased concurrency
Improved backup and recovery services
Difference between file system and DBMS [2]
Both systems contain a collection of data and a set of programs which access that data. A database management system coordinates both the physical and the logical access to the data, whereas a file-processing system coordinates only the physical access.
A database management system reduces the amount of data duplication by ensuring that a physical piece of data is available to all programs authorized to have access to it, whereas data written by one program in a file-processing system may not be readable by another program.
A database management system is designed to allow flexible access to data (i.e., queries), whereas a file-processing system is designed to allow predetermined access to data (i.e., compiled programs).
A database management system is designed to coordinate multiple users accessing the same data at the same time. A file-processing system is usually designed to allow one or more programs to access different data files at the same time. In a file-processing system, a file can be accessed by two programs concurrently only if both programs have read-only access to the file.
Redundancy is control in DBMS, but not in file system.
Unauthorized access is restricted in DBMS but not in file system.
DBMS provide backup and recovery. When data is lost in file system then it not recover.
DBMS provide multiple user interfaces. Data is isolated in file system.
In file system there is no concept of tables orrelationsbetween tables it just organize the records row by row. Database system contains table and relationbetween the tables.
A “File manager” is used to store all relationships in directories in File Systems where as a data base manager (administrator) stores the relationshipin form ofstructural tables.
Disadvantages of database approach
The Database approach too has some disadvantages. They are:
Complexity:
Database management system is an extremely complex piece of software. The users must be familiar with its functionality in-order to make full use of it. Therefore, training for the administrators, designers and users is required.
Size
The database management system consumes a substantial amount of main memory as well as a large amount of disk space in order to make it run efficiently.
Cost of DBMS
A multi-user database management system may be very expensive. Even after the installation, there is a high recurrent annual maintenance cost on the software.
Cost of conversion
When moving from a file-base system to a database system, the company is required to have additional expenses on hardware acquisition and training cost.
Performance
As the database approach is to manage many applications rather than exclusively for a particular one, some applications may not run as fast as before.
Higher impact of a failure
The database approach increases the vulnerability of the system due to the centralization. As all users and applications reply on the database availability, the failure of any component can bring operations to a halt and affect the services to the customer seriously.
Application of database in an organization
A management information system(MIS) is an integrated, user machine system for providing information to support operations, management, analysis, and decision making functions in an organization. The system utilizes computer hardware and software, manual procedures, models for analysis, planning, control and decision making and a data base.
Managers at all levels use similar data. Operating managers require data which is timely, precise, detailed, internal and historical. Upper level managers need data which is aggregated, external as well as internal, future oriented as well as historical and covering a longer span time. An effective MIS cannot be built without viable data management tools.
Any organization has management planning and control activities in the middle and strategic planning and policy making in top management. The database related to an organization contains data relating to the organization, its operations, its plan and its environment that helps in decision making. Transactions record actual results of organizational activities and environmental changes and update the database to maintain a current image.
People in the organization query the database for information to conduct the daily operations. Middle management receives reports comparing actual results to previously recorded plans and expectations. The corporate database provides data for modeling and forecasting which support top management needs. The corporate database supports all levels of an organization and is vital for operations, decision making and the management process.
Network database: This model stores the records with links to other records. Most network database include hierarchical model. This type of database can spread over the geographical area when used in large organization.
Another database application is OLTP (Online Transaction Processing).
Database applicants are any type of company that has customers/clients, keeps stocks of products, provides a service etc. Finance institutions, accountants, estate agents, solicitors, training organizations, schools, colleges, motor dealers, opticians etc. Practically every category of business uses the database system.
Database id used in Universities for student information, course details, and grades. It is used in Airlines for reservations and schedule information. Also in Credit card transactions database approach is used for purchase on credit cards and generations of monthly statements. Apart from this in Human resource database is used for information about employees, salaries, payroll taxes, benefits and for generations of paychecks. In Banking too database is used for customer information, accounts, and banking transactions.
Task 2: The database management system (DBMS) has promising potential advantages. Critically evaluate the advantages and features of database management systems.
Advantages [4]
There are various advantages of introducing database system approach in an application system. Some of them are discussed below:
Control of data redundancy
In the database approach there is central repository of data that not only helps in avoiding the wastage of storage space but also helps in controlling the redundancy by data integration. It helps in avoiding the duplication of data by following techniques like normalization and key concepts. Thus the data is stored in database table at only one place from where it can be retrieved when needed, by avoiding redundancy.
Data consistency
This is maintained by following the concept “control of redundancy”. If the data is stored at one place in a database then while updating any information the changes will be done at only one place which is reflected at all place where ever it is present in whole database. There is no need to change at all places where that data is present. For example if an employee has a change in his address then only in employee table the address will be changed. From there it will be updated every where in database. Thus it ensures all copies of the data are kept consistent. This helps in maintaining consistency of information throughout the system without any loss or misleading of information.
More information from the same amount of data
With the integration of the operated data in the database approach, it may be possible to derive additional information for the same data. All data is stored in a single database, instead of being stored in various other separate files, making the process of obtaining information quicker and in an easy way. For example, in the file-based system of a property company, the Contracts Department does not know who owns a leased property. Similarly, the Sales Department has no knowledge of lease details. Now when we combine these files, the Contracts Department has access to owner details and the Sales Department has access to lease details. Thus more information can be derived now from same available data.
Sharing of data
There is central repository of data in a database system that makes it available to the entire organization and can be shared by all authorized users.
Improved data integrity ….[5]
Data integrity mainly refers to ensuring that data is recorded exactly as intended and when retrieved it’s in the same way as it was when it was recorded. There should not be any data loss when data is retrieved. It mainly provides the validity and consistency of stored data. The database application has various Integrity Constraints, which are consistency rules that the database is not permitted to violate. One of the constraints is specifying data type for every data item. Another is referential integrity constraint in which a record in one file must be related to records in other files. These constraints help in maintaining integrity of data.
Improved security
Database approach provides a protection of the data from the unauthorized users. It may take the term of user names and passwords to identify user type and their access right in the operation including retrieval, insertion, updating and deletion. Providing the facility of accessible rights in database system for various levels in an organization makes it secure for use. For example, the DBA has access to all the data in the database where as a branch manager may have access to all data that is related to only his branch office. In a similar way a sales assistant may have access to all data relating to properties but don’t have any access to sensitive data such as staff salary details.
Enforcement of standards
The integration of the database enforces the necessary standards including data formats, naming conventions, documentation standards, update procedures and access rules. It helps in maintaining standards among the user in an organization. The sharing of data within departments, exchange of information among the users on various projects become easy following the standard database on a centralized environment.
Economy of scale
Using centralized database helps in combining all organization’s operational data into one database with applications to work on one source of data. This helps in cost saving as well as reducing redundancy among the applications. The organizations can invest their money on buying new tools like good processors, storage space and communications devices. Instead of each department buying individually, the organization as whole can do this by saving operational and management time and money.
Balance of conflicting requirements
By having a structural design in the database, the conflicts between users or departments can be resolved. Decisions will be based on the base use of resources for the organization as a whole rather that for an individual entity.
Improved data accessibility and responsiveness
By having integration in the database approach, data accessing can be crossed departmental boundaries. This feature provides more functionality and better services to the users.
Increased productivity
The database approach provides all the low-level file-handling routines. The provision of these functions allows the programmer to concentrate more on the specific functionality required by the users. The fourth-generation environment provided by the database can simplify the database application development.
Improved maintenance
Database approach provides a data independence. As a change of data structure in the database will be affect the application program, it simplifies database application maintenance.
Increased concurrency
Database can manage concurrent data access effectively. It ensures no interference between users that would not result any loss of information nor loss of integrity.
Multiple User Interface
DBMS provides a variety of user interface like query language for casual users, programming language interface for application programmers, command codes for parametric users, menu-driven interface for standalone users. It provides web based GUI interface to database.
Improved backup and recovery services
Modern database management system provides facilities to minimize the amount of processing that can be lost following a failure by using the transaction approach.
References
http://www.gitta.info/IntroToDBS/en/html/DBApproaChar_mehrfachn.html
http://1upto.blogspot.sg/2012/09/list-four-significant-differences.html.
http://databases.about.com/od/administration/a/choosing_a_db.htm
DATABASE SYSTEMS- A Practical approach to design, implementation and management by Thomas Connolly and Carolyn Begg- 4rth Edition
http://www.cvauni.edu.vn/imgupload_dinhkem/file/CSDL/Fundamentals_of_Database_Systems, _6th_Edition.pdf
[http://databases.about.com/od/administration/a/choosing_a_db.htm]
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