Database management System (DBMS)

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by Admin ELearningLine - Thursday, January 14, 2016, 7:46 AM

The DBMS has a number of advantages as compared to ordinary computer file processing approach. The database administrator (as we say DBA) or users must keep in mind these benefits or capabilities during designing databases, coordinating and monitoring the DBMS.

In traditional computer file processing like spread sheets, each application program has its own files or it is just a single file. In this case, the duplicated copies of the same data are created at many places. In DBMS, all related data of an organization is integrated into a single database. The data is recorded at only one place in the database and it is not duplicated. For an example human resource division may have a list of employees and finance division ay have separate list of employees. But we can maintain single data base with all employee details shared between human resource and finance divisions. Hence DBMS helps to control data redundancy. But In DBMS, the data redundancy can be controlled or reduced but is not removed completely. Sometimes, it is necessary to create duplicate copies of the same data items in order to relate tables with each other.

By controlling the data redundancy, the data consistency is obtained. If a data item appears only once, any update to its value has to be performed only once and the updated value (new value of item) is immediately available to all users. If new employee joins your company you don’t need to update finance department files as well as Account department files

In DBMS, data can be shared by authorized users of the organization. The DB Administrator manages the data and gives rights to users or application programs to access the data. Many users can be authorized to access the same set of information simultaneously. The remote users can also share same data. Hence, the data of same database can be shared between different application programs. So you may share same employee database between payroll system as well as human resource management system.

In DBMS, data in database is stored in tables. A single database contains multiple tables and relationships can be created between tables or associated data entities. This makes easy to retrieve and update data. In employee database may store related family information of the employees. Hence that data can be used to define insurance schemes as well.

Integrity constraints or consistency rules can be applied to database so that the correct data can be entered into database. The constraints may be applied to data item within a single record or they may be applied to relationships between records. For an example age of employee cannot be less than 17 years or each employee must have a id number.

Data security is the protection of the database from unauthorized users. Only the authorized persons are allowed to access the database. Some of the users may be allowed to access only a part of database i.e., the data that is related to them or related to their department. Mostly, the DBA or head of a department can access all the data in the database. Some users may be permitted only to retrieve data, whereas others are allowed to retrieve as well as to update data. The database access is controlled by the DBA. He creates the accounts of users and gives rights to access the database.

A operation or transaction in commercial databases is referred to as atomic unit of work. For example, when you purchase something from a point of sale (POS) terminal, a number of tasks are performed such as;

  • Company stock is updated.
  • Amount is added in company’s account.
  • Sales person’s commission increases etc.

All these tasks collectively are called an atomic unit of work or transaction. These tasks must be completed in all; otherwise partially completed tasks are rolled back. Thus through DBMS, it is ensured that only consistent data exists within the database.

In a computer file-based system, if two users are allowed to access data simultaneously, it is possible that they will interfere with each other. For example, if both users attempt to perform update operation on the same record, then one may overwrite the values recorded by the other. Most DBMSs have sub-systems to control the concurrency so that transactions are always recorded with accuracy. For an example two cahiers can issue same item at same time while updating the stock consistently.

In a computer file-based system, the user creates the backup of data regularly to protect the valuable data from damaging due to failures to the computer system or application program. It is a time consuming method, if volume of data is large. Most of the DBMSs provide the ‘backup and recovery’ sub-systems that automatically create the backup of data and restore data if required.

[ Modified: Thursday, January 14, 2016, 7:50 AM ]