DBMS

Database languages are special-purpose languages, which allow one or more of the following tasks, sometimes distinguished as  sublanguages : Data control language  (DCL) – controls access to data; Data definition language  (DDL) – defines data types such as creating, altering, or dropping and the relationships among them; Data manipulation language  (DML) – performs tasks such as inserting, updating, or deleting data occurrences; Data query language  (DQL) – allows searching for information and computing derived information.

The 3-Tier architecture contains another layer between the client and server. In this architecture, client can't directly communicate with the server. The application on the client-end interacts with an application server which further communicates with the database system. End user has no idea about the existence of the database beyond the application server. The database also has no idea about any other user beyond the application. The 3-Tier architecture is used in case of large web application. Fig: 3-tier Architecture

The 2-Tier architecture is same as basic client-server. In the two-tier architecture, applications on the client end can directly communicate with the database at the server side. For this interaction, API's like:  ODBC ,  JDBC  are used. The user interfaces and application programs are run on the client-side. The server side is responsible to provide the functionalities like: query processing and transaction management. To communicate with the DBMS, client-side application establishes a connection with the server side. Fig: 2-tier Architecture

In this architecture, the database is directly available to the user. It means the user can directly sit on the DBMS and uses it. Any changes done here will directly be done on the database itself. It doesn't provide a handy tool for end users. The 1-Tier architecture is used for development of the local application, where programmers can directly communicate with the database for the quick response.

Types of DBMS Architecture   Database architecture can be seen as a single tier or multi-tier. But logically, database architecture is of two types like:  2-tier architecture  and  3-tier architecture .

The DBMS design depends upon its architecture. The basic client/server architecture is used to deal with a large number of PCs, web servers, database servers and other components that are connected with networks. The client/server architecture consists of many PCs and a workstation which are connected via the network. DBMS architecture depends upon how users are connected to the database to get their request done.

There are following differences between DBMS and File system: DBMS File System DBMS is a collection of data. In DBMS, the user is not required to write the procedures. File system is a collection of data. In this system, the user has to write the procedures for managing the database. DBMS gives an abstract view of data that hides the details. File system provides the detail of the data representation and storage of data. DBMS provides a crash recovery mechanism, i.e., DBMS protects the user from the system failure. File system doesn't have a crash mechanism, i.e., if the system crashes while entering some data, then the content of the file will lost. DBMS provides a good protection mechanism. It is very difficult to protect a file under the file system. DBMS contains a wide variety of sophisticated techniques to store and retrieve the data. File system can't efficiently store and retrieve the data. DBMS takes care of Concurrent access of data using some form of lockin

Cost of Hardware and Software:  It requires a high speed of data processor and large memory size to run DBMS software. Size:  It occupies a large space of disks and large memory to run them efficiently. Complexity:  Database system creates additional complexity and requirements. Higher impact of failure:  Failure is highly impacted the database because in most of the organization, all the data stored in a single database and if the database is damaged due to electric failure or database corruption then the data may be lost forever.

Controls database redundancy:  It can control data redundancy because it stores all the data in one single database file and that recorded data is placed in the database. Data sharing:  In DBMS, the authorized users of an organization can share the data among multiple users. Easily Maintenance:  It can be easily maintainable due to the centralized nature of the database system. Reduce time:  It reduces development time and maintenance need. Backup:  It provides backup and recovery subsystems which create automatic backup of data from hardware and software failures and restores the data if required. multiple user interface:  It provides different types of user interfaces like graphical user interfaces, application program interfaces

It uses a digital repository established on a server to store and manage the information. It can provide a clear and logical view of the process that manipulates data. DBMS contains automatic backup and recovery procedures. It contains ACID properties which maintain data in a healthy state in case of failure. It can reduce the complex relationship between data. It is used to support manipulation and processing of data. It is used to provide security of data. It can view the database from different viewpoints according to the requirements of the user.

Database management system is a software which is used to manage the database. For example: MySQL, Oracle, etc are a very popular commercial database which is used in different applications. DBMS provides an interface to perform various operations like database creation, storing data in it, updating data, creating a table in the database and a lot more. It provides protection and security to the database. In the case of multiple users, it also maintains data consistency.

One way to classify databases involves the type of their contents, for example:  bibliographic , document-text, statistical, or multimedia objects. Another way is by their application area, for example: accounting, music compositions, movies, banking, manufacturing, or insurance. A third way is by some technical aspect, such as the database structure or interface type. This section lists a few of the adjectives used to characterize different kinds of databases. An  in-memory database  is a database that primarily resides in  main memory , but is typically backed-up by non-volatile computer data storage. Main memory databases are faster than disk databases, and so are often used where response time is critical, such as in telecommunications network equipment. An  active database  includes an event-driven architecture which can respond to conditions both inside and outside the database. Possible uses include security monitoring, alerting, statistics gathering and authorization. Many

Formally, a "database" refers to a set of related data and the way it is organized. Access to this data is usually provided by a "database management system" (DBMS) consisting of an integrated set of computer software that allows  users  to interact with one or more databases and provides access to all of the data contained in the database (although restrictions may exist that limit access to particular data). The DBMS provides various functions that allow entry, storage and retrieval of large quantities of information and provides ways to manage how that information is organized. Because of the close relationship between them, the term "database" is often used casually to refer to both a database and the DBMS used to manipulate it. Outside the world of professional  information technology , the term  database  is often used to refer to any collection of related data (such as a  spreadsheet  or a card index) as size and usage requirements typically n