Backups : Transaction Processing

Backups for a transaction processing system are produced in a different way to those for a batch processing system. At the end of each time period a backup copy of the master file is made. The time period between each backup could be a day or a week. Making a complete copy of the master file like this is known as file dumping. The copy of the master file is known as a file dump.

Every time an alteration is made to the master file, since the last backup was made, details of the alteration are stored in a transaction log file.

If the system breaks down then two things happen :

• The most recent file dump of the master file is restored to replace the corrupt current master file. This contains all of the lost data except any new transactions made since the backup.
• The transaction log file is used to update the restored master file so that any transactions made since the file dump was produced are restored.

By following this process no data should be lost. If there was no transaction log file then all of the transactions since the last file dump would be lost.

GCSE ICT Companion 04 - (C) P Meakin 2004