Definition
In addition to user data, a database system typically holds a large amount of data. For instance, it keeps metadata—information about data—so that it may be quickly found and retrieved. Once a set of metadata is saved in a database, it might be challenging to update or change. However, as a database management system grows, it must adapt over time to meet user needs. It would become a laborious and extremely complicated task if all of the data were dependent.
Types of data independence in DBMS
There are two types of data independence in DBMS
1. Logical Data Independence
Logical data is information about databases; that is, it contains information on the internal management of data. For instance, a database table (relation) with all of its constraints applied to it. One sort of method that frees itself from actual data stored on the disk is called logical data independence. Any modifications we make to the table format shouldn't affect the data stored on the disk.
2. Physical Data Independence
The real data is kept on the disk in bit format, and all of the schemas make sense. The ability to alter physical data without affecting the schema or logical data is known as physical data independence. For instance, if we wish to upgrade or modify the storage system itself—let's say we want to go from hard drives to SSDs—it shouldn't affect the logical data or schemas in any way.
Difference between Physical and Logical Data Independence
1. Basics
The primary focus of physical data independence is the way that data is kept in a system.On the other hand,the concept of logical data independence primarily addresses how data is defined and organized within a system.
2. Retrieval Simplicity
Retrieving physical data independence is comparatively simple.On the other hand, the logical structure of the data is more important than its physical location, retrieving logical data independence is more challenging.
3. Ease of Implementation
Compared to logical data independence, physical data independence is simpler to achieve. On the other hand, compared to physical data independence, logical data independence is more difficult to achieve.
4. Degree of changes required
It is not required that modifications made at the physical level be reflected at the application level .On the other hand, it is not required that modifications made at the physical level be reflected at the application level.
5. Internal Modification
In order to improve system performance, internal changes could be necessary in physical data independence .On the other hand, whether or not changes to the database structure are required, logical changes must be made in logical data independence.
6. Types of Schema
The internal schema is the main subject of attention in physical data independence. On the other hand, the conceptual schema is the main subject of attention in logical data independence.
7. Examples
Changing hashing algorithms, moving storage devices, and altering data compression techniques are a few examples of physical data independence. As an illustration, consider changing, deleting, or adding an attribute to a system in logical data independence.
