Database Management System

 Database management system

A database management system (DBMS) is a software package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators (DBAs) and other specialists. A database is an integrated collection of data records, files, and other objects. A DBMS allows different user application programs to concurrently access the same database. DBMSs may use a variety of database models, such as the relational model or object model, to conveniently describe and support applications. It typically supports query languages, which are in fact high-level programming languages, dedicated database languages that considerably simplify writing database application programs. Database languages also simplify the database organization as well as retrieving and presenting information from it. A DBMS provides facilities for controlling data access, enforcing data integrity, managing concurrency control, and recovering the database after failures and restoring it from backup files, as well as maintaining database security.

 Database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Database servers are usually multiprocessor computers, with generous memory andRAID disk arrays used for stable storage. Hardware database accelerators, connected to one or more servers via a high-speed channel, are also used in large volume transaction processing environments. DBMSs are found at the heart of most database applications. DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standardoperating system to provide these functions.

Components:-

Ø  DBMS engine accepts logical requests from various other DBMS subsystems, converts them into physical equivalents, and actually accesses the database and data dictionary as they exist on a storage device.

Ø  Data definition subsystem helps the user create and maintain the data dictionary and define the structure of the files in a database.

Ø  Data manipulation subsystem helps the user to add, change, and delete information in a database and query it for valuable information. Software tools within the data manipulation subsystem are most often the primary interface between user and the information contained in a database. It allows the user to specify its logical information requirements.

Ø  Application generation subsystem contains facilities to help users develop transaction-intensive applications. It usually requires that the user perform a detailed series of tasks to process a transaction. It facilitates easy-to-use data entry screens, programming languages, and interfaces.

Ø  Data administration subsystem helps users manage the overall database environment by providing facilities for backup and recovery, security management, query optimization, concurrency control, and change management.

The advantages of DBMS:-

Ø  It represents complex relationships among different data items. 

Ø  Keeps a tight control on data redundancy. 

Ø  Enforces user defined rules to ensure the integrity of data in a table form. 

Ø  Maintains data dictionary for the storage of information pertaining to data fields and data manipulation. 

Ø  Ensures that data can be shared across all applications. 

Ø  Enforces data access authorization. 

Ø  Has an automatic intelligent backup and recovery procedure of data. 

Ø  Has different interfaces through which users can manipulate data.

The functions of Database Management

System(DBMS) are as follows -

Ø  Data Definition - The DBMS must be able to accept data definitions in the source form and convert them to appropriate object form . In other words , the DBMS must include DDL processor or DDL compiler components for each of the various data definition languages (DDLs) .

Ø  Data Manipulation - The DBMS must be able to handle requests to retrieve , update, or delete existing data in the database or to add new data to the database . In other words , the DBMS must include a DML processor or DML compiler component to deal with the data manipulation language (DML) .

Ø  Optimization and Execution - DML requests , planned or unplanned , must be processed by the optimizer component whose purpose is to determine an efficient way of implementing the requests . The optimized requests are then executed under the control of the run-time manager .

Ø  Data Security and Integrity - The DBMS must monitor user requests and rejects any attempts to violate the security constraints defined by the DBA (Database Administrator) .These tasks can be carried out at compile time or run-time or some mixture of the two .

Ø  Data Recovery and Concurrency - The DBMS ,some other related software component , called the transaction manager or transaction processing monitor must enforce certain recovery and concurrency controls .

Ø  Data Dictionary - The DBMS must provide a data dictionary function . The data dictionary is a database which contains "data about data" (called meta data or descriptor) .

EXAMPLES  OF DATABASE MANAGEMENT SYSTEM

•  Microsoft Access
• MySQL
• Microsoft SQL Server
• Oracle
• FileMaker Pro
• FoxPro
• dBASE