Supporting reliable and atomic transaction management in multidatabase systems

Transaction management in multidatabase systems (MDBSs) is complicated by the autonomy requirement, especially in the case of failure. We demonstrate necessary and sufficient conditions for supporting reliable and atomic transaction management in MDBSs. Most previous work assumes single version histories and conflict serializability; this precludes the use of multiversion scheduling protocols in the local database systems. To deal with multiple versions, it is necessary to extend conflict serializability to one-copy serializability. A decentralized transaction management scheme is presented for use in MDBSs which assumes local histories are one-copy serializable and cascadeless. Only a minimum access restriction is imposed on global update subtransactions. Our scheme not only ensures global serializability in the face of failures, but also ensures freedom from global deadlocks