Transaction Management and Concurrency Control

Goals

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

Topics

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