SEMANTIC ACID PROPERTIES IN MULTIDATABASES USING REMOTE PROCEDURE CALLS AND UPDATE PROPAGATIONS

Global ACID properties (Atomicity, Consistency, Isolation and Durabili ty) may be implemented by using a DDBMS (Distributed Data Base Managem ent System.) However, in this solution data availability is low. Furth er, data may be blocked, i.e. if some data are locked from a remote lo cation, the data cannot always be unlocked when the connection to the data fails. This is not a problem when client/server technology is use d because client/server technology only uses local locks, a reason why multidatabases and client/server technology are widely used in real-l ife distributed systems. However, the trouble with such systems is tha t they have no inherent global ACID properties. The objective of this paper is to illustrate how global semantic ACID properties, enforced b y the transactions themselves, may be implemented on top of client/ser ver technology. This is done to preserve high data availability. The g lobal atomicity property is implemented by using retriable and compens atable subtransactions. The global consistency property must be implem ented by the transactions themselves. The global isolation property is implemented by using countermeasures to isolation anomalies. The glob al durability property is implemented by using the durability property of the local DBMSs. The largest bank in Denmark, Den Danske Bank, has implemented all its applications using methods described in this pape r. (C) 1998 by John Wiley & Sons, Ltd.