Global scheduling for flexible transactions in heterogeneous distributed database systems

A heterogeneous distributed database environment integrates a set of autono mous database systems to provide global database functions. A flexible tran saction approach has been proposed for the heterogeneous distributed databa se environments. In such an environment, flexible transactions can increase the failure resilience of global transactions by allowing alternate (but i n some sense equivalent) executions to be attempted when a local database s ystem fails or some subtransactions of the global transaction abort. In thi s paper, we study the impact of compensation, retry, and switching to alter native executions on global concurrency control for the execution of flexib le transactions. We propose a new concurrency control criterion for the exe cution of flexible and local transactions, termed F-serializability, in the error-prone heterogeneous distributed database environments. We then prese nt a scheduling protocol that ensures F-serializability on global schedules . We also demonstrate that this scheduler avoids unnecessary aborts and com pensation.