Optimistic Methods for Concurrency Control
by H.T. Kung et al.
In this paper, the authors
"hope" for optimistic settings and try to exploit them for concurrency
control in the database management system. The contributions are as
Traditional concurrency control schemes use locking and unlocking of
the objects techniques to enforce concurrency control in data base
systems. This paper takes a significant and radical drift and argues
for optimistic concurrency control relying on backup of the
It optimistically hopes for conflict-free transactions
and cashes on the same to increase concurrency and hardware
The mechanism categorizes life cycle of a transaction into
read, write phases. In read, any updates to the objects are done
locally. They are made global in the write phase after a validation
In the case of traditional techniques, the granularity of locking is
a very critical problem which affects both efficiency of concurrency
and performance of the database system. It is not an obvious problem.
However, this problem completely disappears in optimistic concurrency
Scope for Improvement
However, the proposed mechanisms may result in starvation of
transactions where as the locking techniques based counterparts may
result in deadlocks in the transaction executions.
To break the
starvation problem, some naïve solution is proposed in the paper,
however there is clear need for more efficient solutions, I guess.
A detailed performance analysis of both the techniques is essential to
appreciate the merits and pitfalls of each. The study should consider
per se, the overhead caused by locking and unlocking steps, the
improvement in the achieved concurrency because of optimistic control.
Overall, the optimistic approach is suitable for certain class of
applications only especially that have rare transaction conflicts like
a huge B-tree based database system. As a result, this study introduces
yet another issue for the database designers. They should be able to
“know” more about their database needs before deciding on which
approach to take for concurrency control- pure lock-unlock based, or
optimistic or hybrid approach. This paper opens up an interesting
research area in this direction.