Abstract

Hierarchical concurrency control has been proposed as one possible approach for multidatabase systems. However, to apply this approach, some restrictions must be imposed on the local concurrency control algorithms. The restriction is identified. Based on this restriction, the hierarchical concurrency control approach is formalized and its correctness is proven. A novel global concurrency control algorithm based on this hierarchical approach is also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Highlights

  • A Multidatabase System (MDBS) is a facility that allows access to data stored in multiple autonomous and possibly heterogeneous database systems

  • AB shown in figure 1, an MDBS is composed of a set of pre-existing local database management systems, a set of global transactions, a set of local transactions, a set of Local Transaction Managers (LTMs) and a Global Transaction Manager (GTM)

  • The LTM controls the execution of local transactions and global subtransactions in the local database system, while the GTM controls the execution of the global transactions at the global level

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Summary

Introduction

A Multidatabase System (MDBS) is a facility that allows access to data stored in multiple autonomous and possibly heterogeneous database systems. A general hierarchical approach to concurrency control has been proposed for the autonomous database environment [GP86]. Many global concurrency control algorithms have been recently proposed based on this general approach [Pu88] [AGS87] [Vid87]. This general approach is not suitable for all MDBS environments. A new global concurrency control algorithm based on this general approach is proposed in this paper.

A Transaction Model for MDBS
Global Serializability
Autonomy
The General Approach and Restrictions
The Static Properties of the Existing Concurrency Control Algorithms
The Importance of the Static Properties on Global Concurrency Control
Correctness of the hierarchical approach
Limitations of the Hierarchical Approach
The Site Queue Algorithm
Assumptions
Site Queue Concurrency Control Algorithm
Exposing Serialization Points and Simulating Prepared States
Survey of the Existing Global Concurrency Control Algorithms
Conclusion

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