1.6 Organisation of Data Flashcards
Files
Is a collection of records with common properties
Fixed length field
All records are exactly the same length
Variable length field
The length of each record varies
Master Files
Are a collection of records pertaining to one of the main subjects of an information system.
Transaction file
Is used to hold data during transaction processing, it is later used to update the master file
Sequential file access
Is the access of files in the order that they are stored.
Advantages of Sequential file access
Easy to implement and use
Disadvantages of sequential file access
Slow or inefficient for random access operations when working with large files
Indexed sequential file access
Is either sequential access where the files are accessed in the order they are entered, or it is indexed
Advantages of indexed sequential file access
Can access the files quickly and efficiently if it is properly organised.
Reduces the amount of sequential access used
Disadvantages of indexed sequential file access
Expensive as it requires special operators.
Requires more storage space.
Direct/random file access
Is where data is accessed randomly rather than sequentially
Advantages of direct/random file access
Sorting of the records is not required.
Access the required records immediately
Disadvantages of direct/random file access
Expensive.
Less storage compared to sequential file access
Why do we need file safety procedures?
So that we can minimise the damage caused after the incident
