Storage and retrieval in transaction processing systems for HSC Information Processes and Technology

For 4 marks explain what each backup type does and why combining them benefits the agency.

1. Full backup (weekly). Copies all of the agency's data. It gives a complete restore point but takes a long time and a lot of storage, so doing it only weekly is practical.

2. Partial (incremental) backup (nightly). Copies only the data that changed since the last backup. It is fast and uses little storage, so it can run every night with minimal disruption.

3. Benefit of combining. The agency gets the best of both - frequent nightly partial backups limit how much recent work is lost if data is corrupted (good recovery point), while the weekly full backup provides a complete baseline to restore from. Together they balance speed, storage cost and data safety.

Markers reward defining both types and explaining how the combination improves recovery while keeping backups efficient.

"Discuss" at 4 marks wants how the procedure works plus its advantages and limitations for the medical centre.

How it works: three generations of backup are kept. The most recent is the "son," the previous is the "father," and the oldest is the "grandfather." Each new backup becomes the son, the old son becomes the father, and so on, with the oldest cycled out.

Advantages: if the current data is corrupted, the centre can roll back to an earlier intact generation, so patient records can be recovered. Keeping three versions protects against a fault that is only discovered after a backup has already overwritten one copy.

Limitations: it uses more storage media, and because backups are periodic, any changes made since the last backup (for example today's consultations) could still be lost. For sensitive medical data, security of the stored copies is also a concern.

Markers reward explaining the rotation of three generations and weighing recovery benefit against storage and data-loss limits.

For 3 marks describe two suitable backup media and why each fits a daily store backup.

1. External hard disk drive (or SSD). High capacity and fast read/write, so the day's sales data is backed up quickly. It can be disconnected and stored offsite for safety. Suitable for regular, sizeable daily backups.

2. Cloud / online storage. Data is copied over the internet to a remote data centre. It is automatic, offsite by design (protected against fire or theft at the store), and easily scalable, though it depends on internet access.

Magnetic tape is another valid answer (cheap, high capacity, good for archival backups). Markers reward two named media with a justification of capacity, speed or offsite safety for backing up daily sales data.

For 6 marks explain each procedure and link it to both data security and data integrity.

Mirroring: data is written simultaneously to two (or more) storage devices that hold identical copies.

• Data security: if one disk fails, the mirror still holds the data, so it is not lost - this protects availability.

• Data integrity: both copies stay consistent and current, so the system always has an accurate, complete set of data to work from.

Rollback: if a transaction fails part-way or an error occurs, the system uses a log to undo the incomplete changes and return the database to its last consistent state.

• Data integrity: it prevents partial or corrupt transactions from leaving the data in an invalid state, keeping records accurate and complete.

• Data security: combined with the transaction log, it allows recovery to a known good point after a failure or attack.

Conclude that mirroring guards against media failure while rollback guards against transaction failure; together they protect both the safety and accuracy of the data. Markers reward defining each procedure and explicitly tying both to security and integrity.