| Date | November 2020 | Marks available | 2 | Reference code | 20N.2.SL.TZ0.2 |
| Level | SL | Paper | 2 | Time zone | no time zone |
| Command term | Outline | Question number | 2 | Adapted from | N/A |
Question
Billetmania is an online company that sells tickets for theatre performances and music concerts. After a customer has chosen their seats, they can pay for the tickets through a secure online payment system. Once the transaction has been completed, the customer receives an email receipt.
An information system and a database are used for Billetmania’s day-to-day operations.
Define the term database transaction.
Outline how the Billetmania information system would utilize a database.
Explain the importance of transaction durability to Billetmania when clients book tickets.
Explain how the Billetmania database management system ensures that a seat is not booked by two people simultaneously.
Markscheme
Award [1 max].
A logical unit of work that is executed in full or not at all;
A transaction is a single logical operation that comprises of a sequence of database operations;
A transation satisfies the ACID (Atomicity, Consistency, Isolation, Durability) properties;
Award [2 max].
The database would store details of concerts, tickets sold, customers;
An information system would access the database to present data it in a way that aids informs managers / aids decision making (e.g. charts of ticket sales);
Accept any other reasonable example.
Award [3 max].
Durability ensures that transactions are saved permanently and do not accidentally disappear or get erased;
Billetmania does not need to worry the transaction being lost even in the event of power loss, crashes, or errors;
A seat in a theatre is guaranteed even if the database crashes;
Award [4 max].
Concurrency allows multiple users try to book tickets at the same time / complete a transaction at the same time;
Concurrency prevents access by more than one user to the same row/record;
Concurrency uses row locking;
Select seats are locked for a short period of time to ensure that they aren’t double booked/overwritten;
Examiners report
A standard question that was not well answered. Many candidates presented vague responses that did not define the concept of Database Transaction, some of them seemed to have confusion with the concept of Data Migration.
Most candidates were able to outline the role of the database in the given scenario by using correct examples but failed to point out how the information system would utilize the database access.
Some candidates provided detailed responses explaining durability in context by including characteristics of persistence in the event of system failure, but many of the responses were not specific enough and did not correctly relate the response to the given scenario.
Many responses were incomplete and failed to provide a proper explanation. Some of them were very generic. Most candidates were aware of the row locking concept and its application in the given scenario.
