ITPEC FE Morning October 2018 Question 30

Exclusive Control (Locking) — prevents logical contradictions when multiple transactions update the same database simultaneously.

When multiple transactions access shared data concurrently, exclusive control uses locks to ensure only one transaction can modify a resource at a time.

• •Exclusive lock — blocks both reads and writes by other transactions
• •Shared lock — allows concurrent reads but blocks writes

Why not others:
- (b) Integrity constraint — rules on data values (NOT NULL, UNIQUE, FK), not concurrency
- (c) Normalization — eliminates redundancy in table design
- (d) Reorganization — physical storage optimization for performance

Key rule: "Multiple transactions + simultaneous updates + prevent contradictions" → Exclusive control (locking).

AI-generated — may contain errors