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Many popular database management systems implement a multiversion concurrency control algorithm called snapshot isolation rather than providing full serializability based on locking. There are well-known anomalies permitted by snapshot isolation that can lead to violations of data consistency by interleaving transactions that would maintain consistency if(More)
Data warehouses offer a compromise between freshness of data and query evaluation times. However, a fixed preference ratio between these two variables is too undif-ferentiated. With our approach, clients submit a query together with an explicit freshness limit as a new Quality-of-Service parameter. Our architecture is a cluster of databases. The(More)
Many proposals for managing replicated data use sites running the Snapshot Isolation (SI) concurrency control mechanism , and provide 1-copy SI or something similar, as the global isolation level. This allows good scalability, since only ww-conflicts need to be managed globally. However, 1-copy SI can lead to data corruption and violation of integrity(More)
Several common DBMS engines use the multi- version concurrency control mechanism called Snapshot Isolation, even though application programs can experience non- serializable executions when run concurrently on such a platform. Several proposals exist for modifying the application programs, without changing their semantics, so that they are certain to(More)
The CORBA standard, together with its service specifications , has gained considerable attention in recent years. The CORBA Object Query Service allows for declarative access to heterogeneous storage systems. We have come up with an implementation of this service called Harmony. The objective of this article is to provide a detailed description and(More)