On the Cost of Lock Inheritance in Lock Managers Supporting Nested Transactions

The exibility of nested transactions is generally provided at the expense of a more complex locking mechanism which must deal with expensive lock inheritance. In this paper, we give a solution for eecient lock inheritance. Our solution does not change the original nested transactions model but does revisit its locking rules using set-oriented semantics. This allows us to trade the cost of lock propagation at sub-transaction commit for a potentially more complex connict detection. Then we propose an eecient lock implementation which maintains the overhead of lock requests comparable to the traditional overhead in at transactions. We conducted a number of comparative measurements in order to evaluate our trade-oo. Our benchmarks show a cut oo from 7% to 60% of the global time spent in lock operations, which includes lock requests, locks inheritance and release of locks.