Functionally Specified Distributed Transactions in Co-operative Scenarios

Addresses the problem of specifying co-operative, distributed transactions in a manner that can be subject to verification and testing. Our approach combines the process-algebraic language LOTOS and the object-oriented database modelling language TM to obtain a clear and formal protocol for distributed database transactions meant to describe co-operation scenarios. We argue that a separation of concerns, namely the interaction of database applications on the one hand and data modelling on the other, results in a practical, modular approach that is formally well-founded. An advantage of this is that we may vary over transaction models to support the language combinatio

TOPAZ:a tool kit for the assembly of transaction managers for non-standard applications

'Advanced database applications', such as CAD/CAM, CASE, large AI applications or image and voice processing, place demands on transaction management which differ substantially from those in traditional database applications. In particular, there is a need to support 'enriched' data models (which include, for example, complex objects or version and configuration management), 'synergistic' cooperative work, and application- or user-supported consistency. Unfortunately, the demands are not only sophisticated but also diversified, which means that different application areas might even place contradictory demands on transaction management. This paper deals with these problems and offers a solution by introducing a flexible and adaptable tool kit approach for transaction management

Transaktionen in föderierten Datenbanksystemen unter eingeschränkten Isolation Levels

Atomarität und Isolation von Transaktionen sind Schlüsseleigenschaften fortgeschrittener Anwendungen in föderierten Systemen, die aus verteilten, heterogenen Komponenten bestehen. Während Atomarität von praktisch allen realen Systemen durch das Zweiphasen- Commitprotokoll gewährleistet wird, unterstützt kein System eine explizite föderierte Concurrency Control. In der Literatur wurden zwar zahlreiche Lösungsansätze vorgeschlagen, doch sie haben wenig Einfluss auf Produkte genommen, weil sie die weitverbreiteten Isolation Levels nicht berücksichtigen, die Applikationen Optimierungsmöglichkeiten auf Kosten einer eingeschränkten Kontrolle über die Konsistenz der Daten erlauben. Diese Arbeit vergleicht zunächst existierende Definitionen für Isolation Levels und entwickelt eine neuartige, formale Charakterisierung für Snapshot Isolation, dem Isolation Level des Marktführers Oracle. Anschließend werden Algorithmen zur föderierten Concurrency Control vorgestellt, die beweisbar auch unter lokaler Snapshot Isolation die korrekte Ausführung föderierter Transaktionen gewährleisten, und Isolation Levels für föderierte Transaktionen diskutiert. Die Algorithmen sind in ein prototypisches föderiertes System integriert. Performancemessungen an diesem Prototyp zeigen ihre praktische Einsetzbarkeit.Atomicity and isolation of transactions are key requirements of advanced applications in federated systems consisting of distributed and heterogeneous components. While all existing federated systems support atomicity using the two-phase commit protocol, they lack support for federated concurrency control. Many possible solutions have been proposed in the literature, but they failed to make impact on real systems because they completely ignored the widely used concept of isolation levels, which offer optimization options to applications at the cost of less rigorous control over data consistency. This thesis compares existing definitions for isolation levels and develops a new characterization for Snapshot Isolation, an isolation level provided by Oracle, the market leader in the database field. We present algorithms for federated concurrency control that provably guarantee the correct execution of federated transactions even under local Snapshot Isolation, and discuss isolation levels for federated transactions. The algorithms are integrated into a federated system prototype. Performance measurements with this prototype show the practical viability of the developed methods

Transaktionen in föderierten Datenbanksystemen unter eingeschränkten Isolation Levels

Atomarität und Isolation von Transaktionen sind Schlüsseleigenschaften fortgeschrittener Anwendungen in föderierten Systemen, die aus verteilten, heterogenen Komponenten bestehen. Während Atomarität von praktisch allen realen Systemen durch das Zweiphasen- Commitprotokoll gewährleistet wird, unterstützt kein System eine explizite föderierte Concurrency Control. In der Literatur wurden zwar zahlreiche Lösungsansätze vorgeschlagen, doch sie haben wenig Einfluss auf Produkte genommen, weil sie die weitverbreiteten Isolation Levels nicht berücksichtigen, die Applikationen Optimierungsmöglichkeiten auf Kosten einer eingeschränkten Kontrolle über die Konsistenz der Daten erlauben. Diese Arbeit vergleicht zunächst existierende Definitionen für Isolation Levels und entwickelt eine neuartige, formale Charakterisierung für Snapshot Isolation, dem Isolation Level des Marktführers Oracle. Anschließend werden Algorithmen zur föderierten Concurrency Control vorgestellt, die beweisbar auch unter lokaler Snapshot Isolation die korrekte Ausführung föderierter Transaktionen gewährleisten, und Isolation Levels für föderierte Transaktionen diskutiert. Die Algorithmen sind in ein prototypisches föderiertes System integriert. Performancemessungen an diesem Prototyp zeigen ihre praktische Einsetzbarkeit.Atomicity and isolation of transactions are key requirements of advanced applications in federated systems consisting of distributed and heterogeneous components. While all existing federated systems support atomicity using the two-phase commit protocol, they lack support for federated concurrency control. Many possible solutions have been proposed in the literature, but they failed to make impact on real systems because they completely ignored the widely used concept of isolation levels, which offer optimization options to applications at the cost of less rigorous control over data consistency. This thesis compares existing definitions for isolation levels and develops a new characterization for Snapshot Isolation, an isolation level provided by Oracle, the market leader in the database field. We present algorithms for federated concurrency control that provably guarantee the correct execution of federated transactions even under local Snapshot Isolation, and discuss isolation levels for federated transactions. The algorithms are integrated into a federated system prototype. Performance measurements with this prototype show the practical viability of the developed methods

Transactional actors in cooperative information systems

Transaction management in advanced distributed information systems is a very important issue under research scrutiny with many technical and open problems. Most of the research and development activities use conventional database technology to address this important issue. The transaction model presented in this thesis combines attractive properties of the actor model of computation with advanced database transaction concepts in an object-oriented environment to address transactional necessities of cooperative information systems. The novel notion of transaction tree in our model includes subtransactions as well as a rich collection of decision making, chronological ordering, and communication and synchronization constructs for them. Advanced concepts such as blocking/ non_blocking synchronization, vital and non_vital subtransactions , contingency transactions, temporal and value dependencies, and delegation are supported. Compensatable subtransactions are distinguished and early commit is accomplished in order to release resources and facilitate cooperative as well as longduration transactions. Automatic cancel procedures are provided to logically undo the effects of such commits if the global transaction fails. The complexity and semantics-orientation of advanced database applications is our main motivation to design and implement a high-level scripting language for the proposed transaction model. Database programming can gain in performance and problem-orientation if the semantic dependencies between transactions can be expressed directly. Simple and flexible mechanisms are provided for advanced users to query the databases, program their transactions accordingly, and accept weak forms of semantic coherence that allows for more concurrency. The transaction model is grafted onto the concurrent obj ect-oriented programming language Sather developed at UC Berkeley which has a nice high-level syntax, supports advanced obj ect-oriented concepts, and aims toward performance and reusability. W have augmented the language with distributed programming facilities and various types of message passing routines as well as advanced transactions management constructs . The thesis is organized in three parts. The first part introduces the problem, reviews state of the art, and presents the transaction model. The second part describes the scripting language and talks about implementation details. The third part presents the formal semantics of the transaction model using mathematical notations and concludes the thesis