Backups : Introduction

No-one likes losing data that they have entered into a computer. Lost data represents a waste of time and effort. For companies the loss of data can be especially serious. Many companies store essential information such as customer accounts or stock databases on computer. Loss or corruption of this information could cost a company a lot of money.

If data is very important then appropriate security measures should be put in place to try and avoid any data loss or corruption. However problems can still occur :

• An employee could accidentally delete a file or a storage device could fail resulting in data being completely lost.
• Data could be changed accidentally. For example an employee may incorrectly update a set of records in a database. A virus could deliberately change the contents of a file.

Therefore extra copies of important data should be made on a regular basis. These copies are known as backups. If the original files become corrupt then the data can be restored from a backup copy. A company should have a backup strategy which sets out how backups will be made.

Often the method used to make backups will depend upon the type of processing that is being carried out :

Backups by Type of Processing
Batch Processing		Backups are kept using the Ancestral or Grandfather-Father-Son system.
Transaction Processing		Periodically a copy of the master file called a file dump is made. Recent transactions are stored in a transaction log file.
Real-time Processing		A lot of backup hardware is employed to reduce the risk of failure.

A backup is not the same thing as an archive. An archive is a file containing old data which is no longer used but which must be kept. Archive files are often kept under the same conditions as backups.

GCSE ICT Companion 04 - (C) P Meakin 2004