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vaida-abstract
Abstract - Ph D thesis Sanny Syberfeldt
Optimistic Replication with Forward Conflict Resolution in
Distributed Real-Time Databases
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In this thesis a replication protocol - PRiDe - is presented, which
supports optimistic replication in distributed real-time databases with
deterministic detection and forward resolution of transaction
conflicts. The protocol is designed to emphasize node autonomy,
allowing individual applications to proceed without being affected by
distributed operation. For conflict management, PRiDe groups
distributed operations into generations of logically concurrent and
potentially conflicting operations. Conflicts between operations in a
generation can be resolved with no need for coordination among nodes,
and it is shown that nodes eventually converge to mutually consistent
states. A generic framework for conflict resolution is presented that
allows semantics-based conflict resolution policies and
application-specific compensation procedures to be plugged in by the
database designer and application developer.
It is explained how transaction semantics are supported by the
protocol, and how applications can tolerate exposure to temporary
database inconsistencies. Transactions can detect inconsistent reads
and compensate for inconsistencies through callbacks to
application-specific compensation procedures. A tool - VADer -
has been constructed, which allows database designers and application
programmers to quickly construct prototype applications, conflict
resolution policies and compensation procedures. VADer can be used to
simulate application and database behavior, and supports run-time
visualization of relationships between concurrent transactions. Thus,
VADer assists the application programmer in conquering the complexity
inherent in optimistic replication and forward conflict resolution.
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