File Organisation in DBMS

Definition

• File organization refers to the way or techniques that give how the data is structured and stored within computer files or database files.

Characteristics

• There are various file organization methods exist to store data in files, each designed to optimize data retrieval, storage efficiency, and ease of access.
• File organization involves various methods of arranging and managing data within files in the memory to facilitate efficient storage, retrieval, and manipulation.
• Sequential file organization is suitable for logs or data that are processed continuously.

Types of File Organisation Methods

• The choice of file organization depends on various factors, including the type of data, access patterns, system requirements, and performance considerations.
• There are some common file organization methods and each method has its advantages and limitations, making it crucial to select the most suitable one for specific data storage and retrieval needs.:-

1. Sequential File Organization:

• • In this file Organisation, Data is stored in sequential order, one after another, often in a continuous manner.
  • Here, data is accessed sequentially, from the beginning to the desired location.
  • This file organization is suited for batch processing where data is processed linearly.
  • Examples: Text files, log files, and magnetic tapes.

2. Indexed Sequential File Organization:

• • This organization uses an index structure to facilitate both sequential and direct access to data.
  • The Index structure of this file helps to speed up access to specific records.
  • This file uses a combination of accessing methods i.e. sequential and indexed access methods. Hence it is also called Indexed Sequential Access Methods(ISAM). Thus, ISAM allows both sequential access and direct access using an index or a key.
  • This file structure is efficient for applications requiring both sequential and direct access.
  • Example: Database files with indexing structures.

3. Random (Direct) File Organization:

• • In this file organization, Data is stored in fixed-size blocks, and each block is assigned an address.
  • This method allows direct access to any data block by specifying its address, enabling faster retrieval of data.
  • This file organization is commonly used in databases and file systems where rapid access to specific data is crucial.
  • Example: Indexed files, hash-based storage.

4. Hashing File Organization:

• • This file utilizes a hashing function or techniques to compute addresses of data stored in the memory.
  • This method enables direct access to data based on a calculated hash value/address.
  • This method is ideal for quickly locating specific records without sequential scanning.
  • Example: Hash tables in programming, hash-based file systems.

5. Clustered File Organization:

• • This file organization groups related records together physically on storage media.
  • This file organization optimizes retrieval by storing related data in the same or nearby clusters.
  • This file organization is suitable for applications where data often accessed together is physically grouped.
  • Example: File systems organize files into clusters on a disk.

6. (B and B+)Tree-Structured File Organization:

• • This file organizes data in a hierarchical tree-like structure.
  • It supports efficient hierarchical navigation and retrieval of data.
  • This method is used in hierarchical storage systems or file systems.
  • Example: Directory structures in file systems, XML data organization.