1.4.Characteristics of database approach:

The characteristics of database approach are

1.    Self-describing nature of a database system

2.    Insulation between programs and data, and data abstraction

3.    Support of multiple views of the data

4.    Sharing of data and multi-user transaction processing

1. Self-Describing Nature of a Database System

A fundamental characteristic of the database approach is that the database system contains not only the database itself but also a complete definition or description of the database structure and constraints.  This definition is stored in the DBMS catalog, which contain information such as the structure of each file, the type and storage format of each data item, and various constraints on the data. The information stored in the catalog is called meta-data, and it describes the structure of the primary database

               

2. Insulation between Programs and Data, and Data Abstraction

In traditional file processing, the structure of data files is embedded in the application programs, so any changes to the structure of a file may require changing all programs that access this file. By contrast, DBMS access programs do not require such changes in most cases. The structure of data files is stored in the DBMS catalog separately from the access programs. We call this property program-data independence.            

In DBMS environment we just need to change the description of STUDENT record in catalog to reflect add new data item Date of Birth.

In object oriented database management System we write operational methods, where the user can get the functionality without knowing the implementation code this property is called as Operational Independence.

Data Abstraction in DBMS is support for program –data independence, Operational Independence.

Data Abstraction: The characteristic that allows program data independence and program operation independence is called data abstraction. DBMS provides essential information to a user by hiding the internal details

3. Support of Multiple Views of the Data

A database typically has many users, each of whom may require a different perspective or view of the database. A view may be a subset of the database or it may contain virtual data that is derived from the database files but is not explicitly stored. Some users may not need to be aware of whether the data they refer to is stored or derived. A multiuser DBMS whose users have a variety of distinct applications must provide facilities for defining multiple views. For example, student wants to get his exam results, so his number, marks are given as student view which satisfy his need.

4. Sharing of Data and Multiuser Transaction Processing          

A multiuser DBMS must allow multiple users to access the database at the same time. This is essential if data for multiple applications is to be integrated and maintained in a single database. The DBMS must include concurrency control software to ensure that several users trying to update the same data do so in a controlled manner so that the result of the updates is correct.

 For example, when several reservation clerks try to assign a seat on an airline flight, the DBMS should ensure that each seat can be accessed by only one clerk at a time for assignment to a passenger. These types of applications are generally called online transaction processing (OLTP) applications.