Data Independence in Dbms : An Introduction

Data independence in dbms is a property of DBMS which helps you to change the Database schema at one level without disturbing the schema at the next higher level of a database system. Data independence in dbms is of two types.  A database system contains lots of data. For example, it stores metadata, data about data, to find and retrieve data easily. But it is difficult to modify a set of metadata once it is stored in the database. The problem is that when database expands, changes need to be done over time to satisfy the requirements of the users. It would become a highly complex job if the entire data is dependent. In such situation, Metadata follows a layered architecture, so that when user makes the changes in data at one layer, it doesn’t affect the data at another level. Though this data is independent but it is mapped to each other. So this concept is known as data independence in dbms.

Types of Data Independence

There are two types of data independence

1. Logical Data independence

Logical data is data used to describe database. It means this kind of data stores information about how data is managed inside.
For example, a table or relation which is stored in the database and all its constraints, applied on that relation. Logical data independence liberalizes itself from actual data stored on the disk. When user make some changes on table, it should not change the data residing on the disk.

2. Physical Data Independence

The schemas in the database are logical, but the actual data is stored is in bit format on the disk. Physical data independence allows to change the physical data without disturbing the schema or logical data. For example, if user want to upgrade the storage system it means he wants to replace hard-disks with SSD −then this change should not disturb or change the logical data or schemas.