Pessimistic Concurrency Control
悲观并发控制（Pessimistic Concurrency Control, PCC） 指让可能对系统一致性造成影响的 事务 排他地独占资源，其他冲突 事务 只能等待或回滚，是 并发控制 的一种方式。
悲观并发控制 包含：
- 锁（比如：两阶段锁）
- 时间顺序（Timestamp ordering）
Wikipedia
Pessimistic - Block an operation of a transaction, if it may cause violation of the rules, until the possibility of violation disappears. Blocking operations is typically involved with performance reduction.[1]
Database System Concepts
In contrast, locking and timestamp ordering are pessimistic in that they force a wait or a rollback whenever a conflict is detected, even though there is a chance that the schedule may be conflict serializable.[2]
Silberschatz, Abraham, Henry F. Korth, and S. Sudarshan. Database System Concepts. Seventh edition. New York, NY: McGraw-Hill, 2020. ↩︎