Performance studies show that traditional semi-join processing methods are sometimes inefficient because of the storage and processing overhead. To remedy this problem, a new semi-join processing method, called one-shot semi-join execution is proposed. This method allows parallel generation of all the semi-join projections, parallel transmission of all the semi-join projections, and parallel execution of all the semi-joins. The authors apply this method to optimize the response time for processing distributed queries. A response time model is established, which considers both data transmission time and local processing time. Based on this model, an efficient query processing algorithm is developed and analyzed.>

A distributed deadlock detection/resolution algorithm is proposed. In this algorithm, when a deadlock cycle is detected, it is resolved by reordering the wait-for relations between pairs of transactions. Therefore, no transaction abortions are necessary to resolve deadlock cycles. This results in fewer messages and smaller transaction response time. The correctness of this abortion-free algorithm is proved. The abortion-free algorithm can be extended to handle read/write lock requests and to distinguish between transaction classes.>

A queueing model is used to approximate static locking in distributed database systems without deadlocks. Then a random graph model to find the deadlock probability of each transaction is proposed. Finally, the above two models are integrated, so that given the transaction arrival rate, the response time and the effective throughput can be calculated.>