Semantics-Based Concurrency Control
Specifications of data contain semantic information that can be exploited to increase concurrency. For example, two insert operations on a multiset object commute and hence, can be executed in parallel; further, regardless of whether one operation commits, the other can still commit. Applying the same rule, two push operations on a stack object do not commute and hence cannot be executed concurrently. Several schemes have been proposed for exploiting the semantics of operations have to provide more concurrency than obtained by the conventional classification of operations as reads orwrites.
In most semantics-based protocols, conflicts between operations is based on commutativity, an operation oiwhich does not commute with other uncommitted operations will be made to wait until these conflicting operations abort or commit. Some protocols use operations’ return value commutativity, wherein information about the results of executing an operation is used in...
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