Thursday, 4 July 2013

File System versus a DBMS, Advantages of a DBMS


Database
A database is simply an organized collection of related data, typically stored on disk, and accessible by possibly many concurrent users. Databases are generally separated into application areas. For example, one database may contain Human Resource (employee and payroll) data; another may contain sales data; another may contain accounting data; and so on. Databases are managed by a DBMS.
DBMS
A Database Management System (DBMS) is a set of programs that manages any number of databases.
database is an organized collection of data. The data is typically organized to model relevant aspects of reality (for example, the availability of rooms in hotels), in a way that supports processes requiring this information (for example, finding a hotel with vacancies).
Database management systems (DBMSs) are specially designed applications that interact with the user, other applications, and the database itself to capture and analyze data. A general-purpose database management system (DBMS) is a software system designed to allow the definition, creation, querying, update, and administration of databases.

Database Management System Vs File Management System

A Database Management System (DMS) is a combination of computer software, hardware, and information designed to electronically manipulate data via computer processing. Two types of database management systems are DBMS’s and FMS’s. In simple terms, a File Management System (FMS) is a Database Management System that allows access to single files or tables at a time. FMS’s accommodate flat files that have no relation to other files. The FMS was the predecessor for the Database Management System (DBMS), which allows access to multiple files or tables at a time (see Figure 1 below)
comparison.jpg

File Management Systems

AdvantagesDisadvantages
Simpler to use
Typically does not support multi-user access
Less expensive·
Limited to smaller databases
Fits the needs of many small businesses and home users
Limited functionality (i.e. no support for complicated transactions, recovery, etc.)
Popular FMS’s are packaged along with the operating systems of personal computers (i.e. Microsoft Cardfile and Microsoft Works)
Decentralization of data
Good for database solutions for hand held devices such as Palm Pilot
Redundancy and Integrity issues
Typically, File Management Systems provide the following advantages and disadvantages: 
The goals of a File Management System can be summarized as follows (Calleri, 2001):
  • Data Management.  An FMS should provide data management services to the application.
  • Generality with respect to storage devices. The FMS data abstractions and access methods should remain unchanged irrespective of the devices involved in data storage.
  • Validity. An FMS should guarantee that at any given moment the stored data reflect the operations performed on them.
  • Protection. Illegal or potentially dangerous operations on the data should be controlled by the FMS.
  • Concurrency. In multiprogramming systems, concurrent access to the data should be allowed with minimal differences.
  • Performance. Compromise data access speed and data transfer rate with functionality.
From the point of view of an end user (or application) an FMS typically provides the following functionalities (Calleri, 2001): 
  • File creation, modification and deletion.
  • Ownership of files and access control on the basis of ownership permissions.
  • Facilities to structure data within files (predefined record formats, etc).
  • Facilities for maintaining data redundancies against technical failure (back-ups, disk mirroring, etc.).
  • Logical identification and structuring of the data, via file names and hierarchical directory structures.

Database Management Systems

Database Management Systems provide the following advantages and disadvantages: 
Advantages
Disadvantages
Greater flexibility
Difficult to learn
Good for larger databases
Packaged separately from the operating system (i.e. Oracle, Microsoft Access, Lotus/IBM Approach, Borland Paradox, Claris FileMaker Pro)
Greater processing power
Slower processing speeds
Fits the needs of many medium to large-sized organizations
Requires skilled administrators
Storage for all relevant data
Expensive
Provides user views relevant to tasks performed

Ensures data integrity by managing transactions (ACID test = atomicity, consistency, isolation, durability)  

Supports simultaneous access 

Enforces design criteria in relation to data format and structure 

Provides backup and recovery controls

Advanced security

The goals of a Database Management System can be summarized as follows (Connelly, Begg, and Strachan, 1999, pps. 54 – 60): 
  • Data storage, retrieval, and update (while hiding the internal physical implementation details)
  • A user-accessible catalog
  • Transaction support
  • Concurrency control services (multi-user update functionality)
  • Recovery services (damaged database must be returned to a consistent state)
  • Authorization services (security)
  • Support for data communication Integrity services (i.e. constraints)
  • Services to promote data independence
  • Utility services (i.e. importing, monitoring, performance, record deletion, etc.)
The components to facilitate the goals of a DBMS may include the following:
  • Query processor
  • Data Manipulation Language preprocessor
  • Database manager (software components to include authorization control, command processor, integrity checker, query optimizer, transaction manager, scheduler, recovery manager, and buffer manager)
  • Data Definition Language compiler
  • File manager

A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database. In a sense, a database resembles a very well-organized electronic filing cabinet in which powerful software, known as a database management system, helps manage the cabinet’s contents.

Advantages of the DBMS:
The DBMS serves as the intermediary between the user and the database. The database structure itself is stored as a collection of files, and the only way to access the data in those files is through the DBMS. The DBMS receives all application requests and translates them into the complex operations required to fulfill those requests. The DBMS hides much of the database’s internal complexity from the application programs and users.
The different advantages of DBMS are as follows.
1. Improved data sharing.
The DBMS helps create an environment in which end users have better access to more and better-managed data. Such access makes it possible for end users to respond quickly to changes in their environment.
2. Improved data security.
The more users access the data, the greater the risks of data security breaches. Corporations invest considerable amounts of time, effort, and money to ensure that corporate data are used properly. A DBMS provides a framework for better enforcement of data privacy and security policies.
3. Better data integration.
 Wider access to well-managed data promotes an integrated view of the organization’s operations and a clearer view of the big picture. It becomes much easier to see how actions in one segment of the company affect other segments.
4. Minimized data inconsistency.
 Data inconsistency exists when different versions of the same data appear in different places. For example, data inconsistency exists when a company’s sales department stores a sales representative’s name as “Bill Brown” and the company’s personnel department stores that same person’s name as “William G. Brown,” or when the company’s regional sales office shows the price of a product as $45.95 and its national sales office shows the same product’s price as $43.95. The probability of data inconsistency is greatly reduced in a properly designed database.
5. Improved data access.
The DBMS makes it possible to produce quick answers to ad hoc queries. From a database perspective, a query is a specific request issued to the DBMS for data manipulation—for example, to read or update the data. Simply put, a query is a question, and an ad hoc query is a spur-of-the-moment question. The DBMS sends back an answer (called the query result set) to the application. For example, end users, when dealing with large amounts of sales data, might want quick answers to questions (ad hoc queries) such as:
- What was the dollar volume of sales by product during the past six months?
- What is the sales bonus figure for each of our salespeople during the past three months?
- How many of our customers have credit balances of $3,000 or more?
6.Improved decision making.
Better-managed data and improved data access make it possible to generate better-quality information, on which better decisions are based. The quality of the information generated depends on the quality of the underlying data. Data quality is a comprehensive approach to promoting the accuracy, validity, and timeliness of the data. While the DBMS does not guarantee data quality, it provides a framework to facilitate data quality initiatives.
7.Increased end-user productivity.
The availability of data, combined with the tools that transform data into usable information, empowers end users to make quick, informed decisions that can make the difference between success and failure in the global economy.

Disadvantages of Database:

Although the database system yields considerable advantages over previous data management approaches, database systems do carry significant disadvantages. For example:
1. Increased costs.
Database systems require sophisticated hardware and software and highly skilled personnel. The cost of maintaining the hardware, software, and personnel required to operate and manage a database system can be substantial. Training, licensing, and regulation compliance costs are often overlooked when database systems are implemented.
2. Management complexity.
Database systems interface with many different technologies and have a significant impact on a company’s resources and culture. The changes introduced by the adoption of a database system must be properly managed to ensure that they help advance the company’s objectives. Given the fact that database systems hold crucial company data that are accessed from multiple sources, security issues must be assessed constantly.
3. Maintaining currency.
To maximize the efficiency of the database system, you must keep your system current. Therefore, you must perform frequent updates and apply the latest patches and security measures to all components. Because database technology advances rapidly, personnel training costs tend to be significant. Vendor dependence. Given the heavy investment in technology and personnel training, companies might be reluctant to change database vendors. As a consequence, vendors are less likely to offer pricing point advantages to existing customers, and those customers might be limited in their choice of database system components.
4. Frequent upgrade/replacement cycles.
DBMS vendors frequently upgrade their products by adding new functionality. Such new features often come bundled in new upgrade versions of the software. Some of these versions require hardware upgrades. Not only do the upgrades themselves cost money, but it also costs money to train database users and administrators to properly use and manage the new features.

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