software-implemented fault masking in distributedsystems.requires the generation of at least three copies of all processes and the insertion of majority voters at each interprocess communication between process tripl...
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ISBN:
(纸本)0818607378
software-implemented fault masking in distributedsystems.requires the generation of at least three copies of all processes and the insertion of majority voters at each interprocess communication between process triples. If the semantics of the receive operator used by the receiver triple indicates waiting for the receipt of messages coming from different sender triples in an indeterministic order, different sequences of message processing by the processes of the receiver triple have to be avoided by execution of an agreement protocol. A protocol is presented to solve the problem of both fault masking and sequence agreement simultaneously, in order to reduce communication overhead with respect to message number as well as message length. The concept of fault masking is a slight modification of an m-protocol that supports sequence agreement by the generation of at least two sender-specific encoded signatures and by execution of acknowledgement and sequence agreement jointly using the same messages. A general classification of voting problems shows that sequence agreement does not require usual protocols for interactive consistency, even in the case of Byzantine faults. This permits a simple fault-detecting centralized solution for sequence agreement.
The author presents an algorithm for maintaining consistency and improving the performance of databases with replicated data in distributed real-time systems. The semantic information of read-only transactions is used...
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ISBN:
(纸本)0818608153
The author presents an algorithm for maintaining consistency and improving the performance of databases with replicated data in distributed real-time systems. The semantic information of read-only transactions is used for improved efficiency, and a multiversion technique is used to increase the degree of concurrency. Related issues, including the consistency of the states seen by transactions, version management, and recovery of replicated data in distributedsystems. are discussed.
We are investigating the problem of ensuring global consistency in the context of distributeddatabasesystems. Our current research effort concentrates on theoretical study of reliability mechanisms such as algorithm...
ISBN:
(纸本)9780897912181
We are investigating the problem of ensuring global consistency in the context of distributeddatabasesystems. Our current research effort concentrates on theoretical study of reliability mechanisms such as algorithm design and performance characterization. In addition, we are building a testbed for evaluating different reliability mechanisms through detailed simulation and actual *** is the key factor in improving the availability of distributeddatabasesystems. A major restriction in using replication is that replicated copies must behave like a single copy. We have developed algorithms for replication control using tokens [2, 5]. The next step of our research in this direction would be to evaluate different partial operation policies which are critical in maintaining the correctness and achieving the high availability of distributeddatabasesystems. Two alternatives are possible when a partition occurs: pessimistic and optimistic. Neither of the two alternatives is superior to the other. Higher availability achieved by an optimistic approach may be penalized during recovery from partition failures, by backing out committed transactions which violate consistency *** if the replication and concurrency control mechanisms are correct and maintain the consistency of the database, the failures of hardware and/or software at the processing site and communication network may destroy the consistency of the database. In order to cope with failures, distributeddatabasesystems.must provide recovery mechanisms. The goal of checkpointing is to save database states on a separate secure device so that the database can be recovered when errors and failures occur. A checkpointing mechanism which does not interfere with the transaction processing in distributed environment is highly desirable for many applications, where restricting transaction activity during checkpointing is not feasible. Our earlier research has resulted in the developme
The following topics are dealt with: fault-tolerant local area networks;distributeddatabasereliability;fault-tolerant distributedsystems.software fault tolerance;and computer system reliability. 26 papers were pres...
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ISBN:
(纸本)0818606908
The following topics are dealt with: fault-tolerant local area networks;distributeddatabasereliability;fault-tolerant distributedsystems.software fault tolerance;and computer system reliability. 26 papers were presented, all of which are published in full in the present proceedings.
The following topics are dealt with: reliable communication;network partition-handling;fault-tolerant systems.object management;concurrency control;reliable transaction management;and design of reliable software. 24 p...
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ISBN:
(纸本)0818605642
The following topics are dealt with: reliable communication;network partition-handling;fault-tolerant systems.object management;concurrency control;reliable transaction management;and design of reliable software. 24 papers were presented, all of which are published in full in the present proceedings.
An analysis is made of a number of interesting actual or potential parallels between the problems and techniques associated with achieving high reliability, and those associated with the provision of security, in dist...
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ISBN:
(纸本)0818606908
An analysis is made of a number of interesting actual or potential parallels between the problems and techniques associated with achieving high reliability, and those associated with the provision of security, in distributed computing systems.
Before the heralded potential of distributed computer systems.can be realized, the system must be made robust in the face of processor failures. Reassigning the work of a failed processor so that system performance de...
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ISBN:
(纸本)0818606908
Before the heralded potential of distributed computer systems.can be realized, the system must be made robust in the face of processor failures. Reassigning the work of a failed processor so that system performance degrades gracefully is one of the most important problems in designing reliable distributedsystems. The authors present an algorithm for reassigning the work of a failed processor that attempts to minimize the increased cost caused by the redistribution. This algorithm is based on a technique known as clustering. The authors also present a comprehensive cost function, and discuss its applicability to 'real' systems.
A replicated database system is a distributeddatabase system in which some data objects are stored redundantly at multiple sites to improve the reliability of the system. Without proper control mechanisms, the consis...
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ISBN:
(纸本)0818606908
A replicated database system is a distributeddatabase system in which some data objects are stored redundantly at multiple sites to improve the reliability of the system. Without proper control mechanisms, the consistency of a replicated database system might be violated. A scheme to increase the reliability as well as the degree of concurrency is described. It allows transactions to operate on a data object if more than one token copies are available. The scheme also exploits the fact that, for recovery reasons, there are two values for one data object. Proof that the proposed scheme guarantees consistency is provided. Some of variations of the scheme are discussed.
This study is concerned with the establishment of a global time base in a distributed real-time system. It is shown that at least two different time references, an approximate global time and an approximate political ...
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ISBN:
(纸本)0818606908
This study is concerned with the establishment of a global time base in a distributed real-time system. It is shown that at least two different time references, an approximate global time and an approximate political time, must be available in each node. The granularity of the global time is determined by the achievable synchronism of the local real-time clocks. The decisive factor for the accuracy of clock synchronization is the variability of the message delay. A quantitative analysis of the achievable accuracy of clock synchronization in systems.with and without a layered communication architecture is presented. Finally, three functions on the approximate global event times are introduced in order to support the causal analysis of events.
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