A Multi-Level Transaction Approach to Federated DBMS Transaction Management

Title A Multi-Level Transaction Approach to Federated DBMS Transaction Management
Author(s) H.-J. Schek, G. Weikum, W. Schaad
Type inproceedings
Booktitle Proc. of the First Int. Workshop on Inter- operability in Multidatabase Systems, (IMS'91)
Organization Institute for Information Systems, ETH Zurich
Month April
Year 1991


Transaction management in federated database management systems (FDBMS) is compared with multi-level transaction management. An FDBMS has global and local transaction management and can therefore be viewed as a multi-level system. Autonomous execution and commit of subtransactions is a key feature in both FDBMS transactions and multi-level transactions. Consequently, in both models some dependencies of lower levels are propagated to the higher level in order to give the global transaction manager enough knowledge about lower-level dependencies. In order to cope properly with local transactions, not present in multi-level transaction models proposed so far, a dynamic conflict relation between global subtransactions is introduced. By exploiting the knowledge about the context of the conflicts between global subtransactions, we derive a weaker form of multi-level serializability that is equivalent to quasi-serializability. Our approach is further extended to exploit the semantics of the high-level operations that correspond to global subtransactions, even in the presence of local transactions. As a consequence, aborts of global transactions must be implemented by compensating subtransactions, and complete (multi-level) serializability is required for the resulting executions. A locking protocol is proposed that allows the coexistence of global multi-level transactions and local transactions, and the required cooperation by the underlying DBMSs is discussed.
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