Coping with value dependency for failure recovery in multidatabase systems

Abstract

Local autonomy is the main impediment to achieving failure atomicity in a multidatabase system since it allows a local database to unilaterally commit or abort a subtransaction. Compensating a committed subtransaction is in general hard to realize due to the complication arising from the propagation of the committed effects. Resubmitting an aborted subtransaction is more realistic since the problems arising from inter-subtransaction dependencies are more predictable than those from propagation of committed effects. However, if such a dependency is cyclic or if it not only involves values but also data items, then the problem becomes more complicated. In this thesis, a failure recovery scheme¹ using resubmission is proposed. The scheme is based on distinguishing the subtransactions into two different types, and employing different strategies for them. As a result, the scheme allows an aborted subtransaction to be restarted. Compared with other failure recovery schemes which also do not rely on compensation, the scheme compromises local autonomy to a lesser extent. In this thesis, different kinds of dependencies are also studied, their impact on the correctness of resubmission method discussed and solutions proposed.