The term blocking factor describes the ratio of logical records to physical records.
A collection of fields or the data items that are used by any application program are called logical records. A unit of storage transfer among the memory and the controller of the device are known as physical record.
The smallest partition of the storage medium that is assigned to the file or the directory is known as allocation unit.
Advantages of small allocation units:
• The little spaces are properly utilized.
• Small directory and the small files can be properly fit in the small waste memory space.
• The effectiveness for accessing the files is increased.
Disadvantages of small allocation units:
• The number for the allocation units of the devices is increased.
• The size of the data structure is increased.
• The execution time for application program is increased.
To make a recovery of the deleted files or a single record from the system, undelete operation is used.
The content of a logically, but not physically, deleted file can be recovered in an undelete operation.