Lesson 4.10.5.1

4.10.5.1 Client server databases Quiz: AQA Computer Science, Unit 10

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.10.5.1, Client server databases: 20 multiple choice questions for the AQA Computer Science (7517), Unit 10: Fundamentals of databases, written with Revision Ninja.

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The 20 questions

  1. What does a client server database system provide?

    • Simultaneous access to the same database by several clients at the same time.
    • A separate full copy of the whole database for each client to edit locally.
    • Access by only one client at a time, to avoid any possibility of conflicts.
    • Storage of data only on each client's local disk and never on the server.

  2. What problem arises when two clients edit the same record at the same time?

    • The foreign keys in the table are converted into primary keys by the database.
    • Updates can be lost, because one change overwrites the other.
    • Both clients are forced to switch to thin-client software before they can continue.
    • The database is deleted automatically by the server to prevent conflicting edits.

  3. Which mechanism stops other clients from editing a record while one client is changing it?

    • Record locking.
    • Normalisation, which reorganises tables into a smaller number of attributes.
    • Data mining, which searches stored records for patterns over a long period.
    • Foreign key checking, which confirms that linked rows still exist in other tables.

  4. What does serialisation achieve in a database?

    • It converts every record into a serial number for storage on the server disk, so that records can be listed in the order they were stored.
    • It encrypts each record before it is sent over the network to a client.
    • It copies the database to a backup server each time any record is changed.
    • It orders concurrent transactions so that the result matches running them one after another.

  5. Which control uses timestamps to decide the order in which conflicting operations are applied?

    • Thin-client rendering, which draws the screen on the server before sending it.
    • Timestamp ordering.
    • Normalisation, which divides data into tables to remove redundancy.
    • Record locking, which prevents other clients from using a record at all.

  6. What is the purpose of concurrency control?

    • To allow clients to read the database only after the server has been stopped.
    • To preserve database integrity when many clients access the same data at the same time.
    • To reduce the amount of data a client is allowed to store on its local device, so that the server holds all the data for the whole network.
    • To make each client see a different version of every table in the database.

  7. What is a record lock?

    • A lock that stops other clients changing a record while one client is editing it.
    • A setting that makes a record permanently read-only for every user of the system.
    • A password that encrypts a single record in the database for security.
    • A backup copy of a record that is stored on a separate server.

  8. Two clients each read a balance of 100. Client A adds 20 and writes 120. Client B subtracts 30 from its copy of 100 and writes 70 without re-reading. What is the final value and why?

    • 90, because both updates were applied in full to the same balance held in the database.
    • 120, because the last write always keeps the larger value of the two records.
    • 70, because Client B's write overwrote Client A's update, so the update was lost.
    • 100, because the database rejects every write from a client that is in conflict with another.

  9. If the two updates of +20 and -30 are serialised, starting from a balance of 100, what is the final balance?

    • 120, which is the result of applying the +20 update and ignoring the -30 update.
    • 110, which is the result of adding 20 and subtracting only 10.
    • 70, which is the result of subtracting 30 without applying the 20 first.
    • 90

  10. A database uses record locking. Client A locks a record, and Client B then requests the same record. What happens to Client B?

    • Client B is given a copy of the record, which it can edit without affecting the database.
    • Client B edits the record at the same time, and the server merges the two versions automatically.
    • Client B is disconnected from the database and must log in again before it can continue.
    • Client B must wait until Client A releases the lock before it can edit the record.

  11. Which problem does timestamp ordering help to prevent?

    • A client being unable to connect to the server because of its IP address setting, which is a network problem and not a database fault.
    • A later operation being applied before an earlier conflicting operation on the same data.
    • A foreign key pointing to a row that does not yet exist in the referenced table.
    • The database running out of disk space during a large import of records.

  12. Why might a server use commitment ordering to control concurrent transactions?

    • To apply the effects of conflicting transactions in the order in which they commit.
    • To encrypt each transaction before it is sent over the network to the client.
    • To let clients connect without any authentication, which saves time for every user.
    • To reduce the number of tables the server must keep on its disk drive.

  13. Which phrase describes several clients using a database at once while the system keeps the data correct?

    • Concurrent access, with integrity controls such as locking or serialisation.
    • Thin-client computing, with local caching of the records on each device.
    • Big Data distributed storage, with records split across several servers.
    • Normalised relational design, with each attribute stored in its own table, so that each client keeps its own copy of the tables it uses.

  14. Which situation is most likely to lead to lost updates?

    • Two clients read a record, then both write back changes with no locking or other control in place.
    • A table with a foreign key that refers to a valid primary key in another table.
    • Clients that connect over a wired network rather than a wireless network to the server.
    • One client reads a record while the server writes a backup of the same record.

  15. A school database lets staff update student records from many devices. Which feature is most important?

    • A larger monitor, so that more records can be displayed on screen at one time.
    • Storing the records in a single text file that every client opens and edits directly.
    • Thick-client software, so that each device stores a full copy of all the records.
    • Concurrency control, so that simultaneous edits do not overwrite each other.

  16. Evaluate: what is a disadvantage of record locks?

    • A client may have to wait, and two clients locking records in opposite order can cause a deadlock.
    • They allow two clients to change the same field at the same time without any risk.
    • They cause the database to store duplicate copies of every record it holds.
    • They remove the need for any backup of the database to be taken regularly.

  17. Why is simultaneous access managed rather than simply allowed?

    • The database stores each client's changes in a separate file until the end of the day.
    • Clients are not permitted to read data, so that writes can be done with safety.
    • Without control, interleaved operations can leave the database in an inconsistent state.
    • Every client must wait for the server to finish all of the other requests first.

  18. Client A and Client B both edit record 5. Which control ensures that B's update is based on the current version of the record?

    • A backup of record 5 taken before any of the edits begin in the session.
    • A composite primary key that combines the record number with the name of the client.
    • A foreign key on the record that points to a table with no rows at all.
    • A timestamp or version check that rejects an update made to a stale copy.

  19. Which statement correctly contrasts record locking with serialisation?

    • Locking blocks access to a record while it is held, whereas serialisation orders conflicting transactions as if run one at a time.
    • Locking is used only for thin clients, whereas serialisation is used only for thick clients.
    • Both are the same technique under two different names used by different database vendors.
    • Serialisation prevents all access to records, whereas locking orders transactions by their timestamps.

  20. Why is a shared client server database more suitable than many separate local copies for a live ticket sales system?

    • Shared databases cannot be accessed by more than one client at a time, so they are safer, since only one client can ever be connected.
    • Local copies cannot store any data, so they are always empty during ticket sales.
    • All clients see the same current data, so the system is less likely to sell the same seat twice.
    • Separate copies are always faster because they never need to communicate with a server.

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