An Asynchronous Differential Join (ADJ) scheme that can maintain join-materialized views in a distributed environment is introduced. The efficiency of the asynchronous data replication can be enhanced by minimizing data to be sent to relevant sites. It also has an advantage in that the scheme prevents huge base tables from being locked by the remote requests through the utilization of differential files. Experimental results show that the faster the communication speed and the lesser the screening factor, the higher the total cost ratio.Request access from your librarian to read this article's full text.

The problem of updating materialized views in distributed database systems is discussed. An architecture and detailed procedures to update a collection of remote views with arbitrary refresh times by using a single differential file are prescribed. The efficiency of the update procedure is enhanced by adopting a multiple-query optimization approach and by introducing a powerful prescreening procedure to eliminate differential tuples. It is shown that even for a single remote view there are many instances where the presented update procedure performs better (with respect to total I/O and communication costs) than existing methods.>

The problem of updating materialized views in distributed database systems is discussed. An architecture and detailed procedures for updating a collection of remote views with arbitrary refresh times by using a single differential file are described. The efficiency of the update procedure is enhanced by adopting s multiquery optimization approach and by introducing a powerful prescreening procedure to eliminate differential tuples. It is shown that even for a single remote view, there are many instances where the update procedure performs better (with respect to total I/O and communication costs) than a base table approach.>

The problem of identifying common subexpressions and using them in the simultaneous optimization of multiple queries is dealt with. In particular, emphasis is placed on the strategy of selecting access plans for single queries and their integration into a global access plan that takes advantage of common tasks. A dynamic programming algorithm is presented for the selection of individual access plans such that the resulting global access plan is of minimum processing cost. The computational complexity of this algorithm represents a significant improvement over existing algorithms.>