| Date | May 2018 | Marks available | 3 | Reference code | 18M.2.SL.TZ0.2 |
| Level | SL | Paper | 2 | Time zone | no time zone |
| Command term | Explain | Question number | 2 | Adapted from | N/A |
Question
ShowTime is a local theatre that allows online booking for its various shows.
All customers are able to access the database to book a movie of their choice.
However, some of the customers have received incorrect information when their booking has been made. This has been caused by update anomalies.
ShowTime have introduced a database recovery system in case the database becomes corrupted.
Identify two types of update anomaly.
Outline two methods of database recovery that can be used to restore the system.
Identify three tasks that are carried out by the database administrator (DBA).
Customers can choose a credit card as their method of payment. However, some customers are concerned that their personal information could get shared with unauthorized third parties.
Explain one way that the DBA at ShowTime can ensure the anonymity of the customers is maintained.
Markscheme
Award up to [2 max].
Insertion;
Deletion;
Modification;
Lost update;
Award [1] for each method of recovery followed by [1] for brief explanation up to a maximum of [2].
Mark as [2] and [2].
Do not accept generic back up responses. It must be DBMS related.
System log;
In the event of a disk crash (any catastrophic failure);
The recovery method recovers a past copy of the database;
Backed up to archival storage and reconstructs a more current state by redoing the operations of committed transactions, up to the time of failure.
Deferred Update;
To support ABORT and machine failure scenarios;
While a transaction runs, no changes made by that transaction are recorded in the Database;
On a commit, new data is recorded in a log file and flushed to the disk;
New data is then recorded in the database itself;
On abort, do not do anything (the database has not been changed);
On a system restart after a system failure, REDO the log;
Data on disk is not updated until after a transaction commits fully;
Award up to [3 max].
Authorizing/managing access to the database;
Coordinating and monitoring its use;
Capacity planning;
Routine backups to safeguard from data loss during crash;
Tried and tested strategies to recover the database after any crash;
reinstallation/overwrite of data; // Do not accept installation of new software alone
Manage security;
Award up to [3 max].
Important sensitive information like personal details such as names, social security;
Number and addresses should be separated;
A unique identifier should be assigned to each customer;
This identifier is then used to access the booking details in the ShowTime;
Note: No generic access rights issues like authorisation should be accepted.
Do not accept Encryption as it is a general point and not specific to DBMS.
