It is increasingly important for organizations to achieve additional coordination of diverse computerized operations. To do so, it is necessary to have database systems that can operate over a distributed network and can encompass a heterogeneous mix of computers, operating systems, communications links, and local database management systems. This paper outlines approaches to various aspects of heterogeneous distributed data management and describes the characteristics and architectures of seven existing heterogeneous distributed database systems developed for production use. The objective is a survey of the state of the art in systems targeted for production environments as opposed to research prototypes.

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A model of a multidatabase system 1s defined m which each local DBMS uses the two-phase lockmg protocol Locks are released by a global transacuon only after the transaction commits or aborts at each local sate Fadures may occur durmg the processmg of transacuons We design a fault tolerant transaction management algorithm and recovery procedures that retam global database consistency We also show that our algorrthms ensure freedom from global deadlocks of any kmd 1. Introduction A multldatabase system (MDBS) 1s a software package that allows user transacaons to mvoke remeval and update commands agamst data located m heterogeneous hardware and software environments. A multi&tabase envronment supports two types of transactions

In an effort to reevaluate Gough's (1954) classic study of common misconceptions about neuroticism, an investigation was undertaken of the degree to which judges could simulate the Basic Personality Inventory (BPI) responses of a clinically depressed patient group. Judgments were recorded of the probability of responding to each of 240 BPI items by a total of 56 university student judges. Judges were assigned randomly to one of two information conditions, one that had only the label “clinical depression” and another that had, in addition, a more extensive definition. Judgmental profiles of depressed patients indicated very high reliabilities (.99) across information conditions, a high association with actual profiles of clinically depressed patients, and differentiation from other psychiatric patients and normal controls. Results were interpreted as supporting the accuracy of judgments of psychopathology, particularly when certain preconditions are met, namely, the use of a meaningful construct of psychopathology and the prediction of behavior relevant to that construct.

A model of a multidatabase system 1s defined m which each local DBMS uses the two-phase lockmg protocol Locks are released by a global transacuon only after the transaction commits or aborts at each local sate Fadures may occur durmg the processmg of transacuons We design a fault tolerant transaction management algorithm and recovery procedures that retam global database consistency We also show that our algorrthms ensure freedom from global deadlocks of any kmd