The aim of producing a backup strategy is to make sure that a computer system can be returned to its original state if data has been lost or corrupted.

A backup strategy is put in place to avoid permanent data loss and to ensure the integrity of stored data i.e can get back to a previous version and build up the data correctly if current data found to be in error.

Factors that should be considered in a backup strategy: Selection of storage medium depends on volume of data Frequency of backup depends on how often the data is updated No. of backup copies kept depends how often data is updated What will be copied; full (all data) or differential (just changes) Recovery procedures; how quickly correct data is needed Location of backup – how secure is this data?

A backup strategy needs a well documented and tested recovery procedure to ensure backup data is restored properly Factors that should be considered in a recovery procedure: A well documented procedure that allocates roles and responsibilities to staff. Availability of alternative hardware and accommodation if the originals have been destroyed. Availability of original software such as the customised operating system and application programs! That up-to-date backup data is readily available

Batch processing systems: Defn: A large number of similar paper documents are typed up onto a transaction tape. The transaction tape updates the master file at a regular set time. Eg Payroll: timesheets are typed into a transaction file and update the employee master file each Friday night and produce wage cheques and payslips. Timesheet Transact G34 Grand Father Employee master PayrollWeek 34 Father Employee master G35 Timesheet Transact G35 PayrollWeek 35 Son Employee master G36 How would the Son file be regenerated?

Online backup of small/medium interactive transaction systems: Transactions are typed in and processed immediately before the next transaction is entered. Eg Paying a gas bill a business can’t afford to lose even a small amount of data but can lose some operational time while data is restored from backup. There is no prepared transaction tape so the system creates a record on an online transaction log as each transaction is typed in. The master file is backed up every night. Daily Transactio n Log Father / Son Customer Account master Interactive transaction processing If the system crashes the son master file is restored from last nights father backup after adding the days transaction log to it.