Locking Mechanisms
Lock Types
| Lock | Also Called | Purpose | Compatibility |
|---|---|---|---|
| Shared (S) | Read lock | Reading data | Compatible with S |
| Exclusive (X) | Write lock | Writing data | Not compatible with any |
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LearnStep 1 of 2
Locking
Learning Objectives
- •Understand lock types
- •Learn two-phase locking
Lesson Outline
LearnStep 1/2
Locking
Two-Phase Locking (2PL)
Ensures serializability:
Strict 2PL
Hold all exclusive locks until commit/abort:
- Prevents cascading rollbacks
- Most common in practice
Lock Granularity
- Row-level: Most concurrent, highest overhead
- Page-level: Balance
- Table-level: Least concurrent, lowest overhead