Backup Procedures and Media
Transaction Processing Systems
For businesses that use Transaction Processing Systems, they cannot afford transaction data to be lost due to hardware failure or corruption. One the characteristics studied earlier in the unit was that transactions must have durability. That is, a customer should, at any time be able to ask the store to recall the transaction from their database for the purpose of refund, exchange or to honour a warranty claim. Similarly, if a customer has paid a deposit on an item, then the merchant must honour that payment when the customer chooses to pay for the item in full.
To this end, all businesses should employ a method of backup and recovery. Essentially, a backup is simply a copy of files to a separate secondary storage device as a precaution in case the first device fails or data is lost.
There are three different types of backup procedures commonly employed by individuals and organisations. Full Backup Incremental Backups and Differential Backups
Full Backup
A full backup is a complete copy of all data within the system. This could include the entire contents of the hard disk(s), including all the operating system, program files, configurations and of course all the data, For most TPS’, the data is the critical aspect, as the software and configuration of the system rarely changes. To this end, most businesses perform full backups of all their data on a regular basis. A system restore is an easier process from a full backup, should the system fail. The data is simply copied back to its original location; this however can take a long time to perform, especially if the media (drive) that the data was originally on was to fail. This system restore, for large orgainsations may take over a weekend to perform.
Incremental Backup
Incremental backups involve making partial backups that copy all files that have changed or been created since the last backup – the last backup may have been a full or partial backup. An incremental backup is significantly faster and requires significantly less storage compared to that of a full backup. Before an incremental backup, it is necessary to perform a full backup at some stage. I.e The full backup is made, then each day, it compares the previous day’s backup and only updates (backs up) changed or new files.
Whilst there are time advantages at the time of backup, the restoration period is quite involved; first the full backup must be restored, then subsequent partial backups, until all data is restored. Backup Procedures and Media
Transaction Processing Systems
Differential Backup
A differential backup backs up only the files that changed since the last full backup. For example, suppose you do a full backup on Sunday. On Monday you back up only the files that changed since Sunday, on Tuesday you back up only the files that changed since Sunday, and so on until the next full backup. Differential backups are quicker than full backups because so much less data is being backed up. But the amount of data being backed up grows with each differential backup until the next full back up. Differential backups are more flexible than full backups, but still unwieldy to do more than about once a day, especially as the next full backup approaches.
In terms of restoration, a differential backup is easier that an Incremental backup as only the last full backup and the most recent differential backup needs to be applied. The disadvantage is that each differential backup grows in size as each backup is applied. Backup Procedures and Media
Transaction Processing Systems
1 Go to the following links to revise your understanding of the variety of backup procedures. They should include:
Grandfather, Father, Son http://www.mckinnonsc.vic.edu.au/vceit/backups/backup_schemes.htm
Partial Backups, including incremental and differential http://support.microsoft.com/kb/136621 Backup Procedures and Media
Transaction Processing Systems 2 Record which data method you would use for the following applications. Justify your answer
A Bank’s financial records
The Australian Stock Exchange
The School Library Backup Procedures and Media
Transaction Processing Systems Backup Storage Media.
Using the media described in the Wikipedia article http://en.wikipedia.org/wiki/Backup recommend storage media for the following examples:
A small corner store – Woolworths Tahmoor Ticketek.com.au –
Case Study – The School Data Backup Procedure.
Devise a set of questions to ask the IT department about backup at the College. You need to obtain information relating to what you have learnt about backups. You may need to explain to them the different types of backup procedures. Backup Procedures and Media
Transaction Processing Systems Define the following terms and relate their definition to the context of a Transaction Processing System: grandfather, father, son ...... off-site storage
...... secure on-site storage
...... full and partial backups
Backup Procedures and Media
Transaction Processing Systems ...... recovery testing
...... Backup Procedures and Media
Transaction Processing Systems suitable media
...... specialised backup software
...... transaction logs
...... documenting backup and recovery procedures
...... Backup Procedures and Media
Transaction Processing Systems mirroring ...... rollback ...... Backup Procedures and Media
Transaction Processing Systems HSC Question Examples Backup Procedures and Methods in a Transaction Processing System
Syllabus reference: Students learn about: data backup and recovery, including: – grandfather, father, son – off-site storage – secure on-site storage – full and partial backups – recovery testing – suitable media – specialised backup software – transaction logs – documenting backup and recovery procedures – mirroring – rollback 2001 HSC
Question 25 — Transaction Processing Systems (20 marks) Use a SEPARATE writing booklet.
(a) (i) Discuss the advantages of a ‘grandfather, father, son’ backup procedure.
2002 HSC
A video store is considering installing a ‘self-checkout’ system where customers can borrow videos by scanning their membership cards and videos and pay by EFTPOS. A ‘self-checkout’ transaction has three steps: • membership validation; • borrowing limit check; • payment processing. For membership validation the barcode on the membership card is used to access the member database to find a match. The customer proceeds to the scanning of videos if the membership is valid, otherwise a message is displayed. Using the video barcode data and details from the member database, the system checks that no more than six videos are borrowed. A message is displayed if the limit is exceeded. Payment processing involves the calculation of borrowing charges, the scanning of the customer’s EFTPOS card, the entry of a personal identification number and the electronic communication of these details to the financial institution. Video charges are obtained from the video database via the video barcodes. Transaction details are written to the transaction file for each video borrowed. (ii) Discuss appropriate backup procedures for the proposed system. Backup Procedures and Media
Transaction Processing Systems
2004 HSC
One of Australia’s largest organisations recently conducted the country’s biggest e-voting project, allowing its 2 million members to vote via the internet. Each voter was sent a personal identification number (PIN) by post. The voter logged onto a secure website with his/her membership number and PIN before the voting deadline. The e-voting system checked that the user had completed all voting details correctly according to voting rules. Once the vote was accepted, the voter’s details were ‘tagged’ to prevent multiple voting, and a confirmation was generated for the voter. (c) (i) Outline backup procedures suitable for this e-voting transaction processing system so that no votes will be lost in the event of a system failure.