Application Specific Transaction Management in MultidatabaseSystems

  • Authors:

  • Peter Muth

  • Affiliations:

  • Department of Computer Science, University of the Saarland, P.O. Box 151150, D-66041 Saarbrücken, Germany. E-mail: muth@cs.uni-sb.de

  • Venue:
  • Distributed and Parallel Databases
  • Year:
  • 1997

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Abstract

We present a transaction model for multidatabase systems withautonomous component systems, coined heterogeneous 3-level transactions. Ithas become evident that in such a system the requirements of guaranteeingfull ACID properties and full local autonomy can not be reconciled. In theheterogeneous 3-level transaction model, semantics of actions and specificproperties of the architecture of multidatabase systems and of applicationsare utilized to define application specific compromises between thesecompeting goals. We consider different definitions of conflicts betweenactions together with application specific sets of allowed (autonomous)local transactions and global subtransactions. A formal model forserializability is given. It is proven that heterogeneous 3-leveltransactions guarantee all consistency constraints that are ensured inserial executions. In contrast to most other models, we do not require datato be partitioned into global and local data. In particular, heterogeneous3-level transactions even allow the same data to be updated by local andglobal transactions in parallel, if these updates are found to besemantically non-conflicting.Recovery is handled by inverse actions.We present a formal framework for this approach which is fully integratedinto serializability theory by considering inverse actions as ordinaryactions. This has an important impact on the relationship of concurrencycontrol and recovery in our model: By changing the definition of conflictsbetween actions in order to tailor the model according to application needs,recovery is implicitly affected and no further explicit adaptation ofrecovery algorithms is necessary.The heterogeneous 3-level transaction model assumes component databasesystems to support ACID transaction properties. Further properties of localtransactions or interfaces of the component database systems are notrequired. We describe a prototype implementation of heterogeneous 3-leveltransactions in the object-oriented database system VODAK.