An extended transaction model for multidatabase systems

Transaction management in multidatabase systems presents numerous challenges due to the heterogeneity of the underlying databases and the need to preserve autonomy of local. systems. On the other hand, the existence of multiple databases frequently makes it possible to accomplish the objective of a transaction by performing an action in one of several. functionally equivalent databases. This property of multidatabase systems will be referred to as function replication. In this paper, we propose two extensions to the traditional. transaction model for a multidatabase environment. They are: (1) allowing the composition of flexible global transactions by taking advantage of the function replication and (2) providing explicit control of the execution of the subtransactions of a global transaction. In the proposed model, a global transaction can tolerate a site failure by submitting a substitute subtranaaction to another functioning site. We formally define the new transaction model and discuss the scheduling, concurrency control and commitment of the extended multidatabase transactions