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Client server databases
Official AQA 7517 section 4.10.5.
0
Objectives
5
Flashcards
7
Questions
36 min
Study time
AqaA LevelComputer ScienceFundamentals of databases
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Client server databases1 objectives
- Client server databases: Know that a client server database system provides simultaneous access to the database for multiple clients. Know how concurrent access can be controlled to preserve the integrity of the database. Concurrent access can result in the problem of updates being lost if two clients edit a record at the same time. This problem can be managed by the use of record locks, serialisation, timestamp ordering, commitment ordering.
Key terms
Concurrent accessSerialisation
Exam tips
- Link the control method to the concurrency problem: When describing record locks, serialisation, timestamp ordering or commitment ordering, explain how the method controls simultaneous operations and helps prevent a lost update.
Common mistakes
- Confusing a lost update with any failed database operation: A lost update specifically occurs when two clients edit the same record and one saved update overwrites the other.
Practice preview
- What is a key feature of a client server database system?
- Two clients read the same database record. Each client changes the record and then saves it. The second save overwrites the first change. What problem has occurred?
- Which method controls concurrent access by preventing another client from editing a record while it is locked?
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