CS262A Reading Summary 13

Granualarity of Locks and Degrees of Consistency in a Shared Data Base (first section)

J. N. Gray et al
Summary by Feng Zhou
10/3/2002

1. The significance of locking granularity is discussed. It is mainly a trade-off between locking overhead and possible concurrency. Fine-grained locking may allow more concurrency, at the cost of larger locking overhead. And vice versa.
2. A hierarchy protocol of locking, at different data object levels, is presented. The paper starts with a tree structured static model and finally discusses a DAG structured dynamic locking model.
3. Intentional locking is introduced as the result of doing hierarchical locking. Three new locking modes: IS, IX and SIX are introduced and their meaning, compatibility with other S and X modes are discussed. This is very important because it's only with these clear locking protocol, can a complex DBMS system be built to work reliably.

One major flaw:

No evident flaws.