Direct file organization— organization of files based on a unique for each file, which is accessed directly through the memory address of the key. Direct file organization allows data to be retrieved quickly in a random manner, regardless of the way in which the data was originally stored. In this method, the unique key that is used to organize files (such as a social security number) is converted directly to a memory address, using a mathematical formula called a hashing algorithm.
The hash function is applied to determine the block’s address for storing the records in the direct file organization method. So, this file organization method is also known as the Hash file organization. This hash function can be either a simple or complex function of mathematics. This hash function is used on some attributes/columns for getting the block address. These columns can be either key or non-key. Thus, every record is stored randomly whatever may be the order of their coming. So, this file organization method is called random or direct file organization. When the hash function is applied on a key column, the column is known as the hash key, and when the hash function is applied on the non-key column, that column is known as the hash column.