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Related changes should succeed together - Paper 1
Read the information, then answer the questions. An adult may read the instructions aloud. Show your working where asked.
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Isolated reservation model: places=6, enrolments=0. One operation must reduce places by 1 AND create one enrolment together. A failure is injected after the place update but before the enrolment insert. Then a fresh successful attempt performs both steps. These are invented in-memory records, not production instructions.
Worksheet preview
- Starting with 6 places and 0 enrolments, what should be stored after the failed transaction rolls back?
- What should be stored after the later successful transaction? State the consistency rule.
- Would the database rollback automatically undo an already-sent email? What does a transaction not replace?
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