[CMPT 454] Week 8_3

June·2021년 3월 10일

CMPT 454

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Transaction Management and Concurrency Control


  • To enusre correctness for concurrent execution of queries and updates from multiple users.


Concurrent vs non-concurrent data access

Why Have Concurrent Processes?

Data access: R(A) and W(A)

Concurrency increases throughput

T1T2는 concurrency가 없었을 때 상황을 나타내는 표시이다.

Transactions (a single user)

Example of Transactions

결과는 다르지만 acceptable하다는 뜻이다. concurrent하게 스케줄을 실행해서 T1T2 또는 T2T1이 나와야한다.

Schedules (multiple users)

The ACID Properties of Schedules

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