Independently updating copies of a database during a network partition may lead to data inconsistencies and anomalous behavior. To better cope with these problems, we propose principles for the design of the database ...
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ISBN:
(纸本)0818605014
Independently updating copies of a database during a network partition may lead to data inconsistencies and anomalous behavior. To better cope with these problems, we propose principles for the design of the database schema and transactions. The authors also propose a tool (Data-patch) that aids the database administrator in the development of an integration program for database copies that diverged.
Some ideas on the construction of user applications as atomic actions are developed. Atomic actions that last a long time pose several problems if conventional ideas on concurrency control and recovery are applied. Wh...
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Some ideas on the construction of user applications as atomic actions are developed. Atomic actions that last a long time pose several problems if conventional ideas on concurrency control and recovery are applied. What is required is some means of delaying commitment without sacrificing performance. A model is proposed in which it is possible for an action to release and process as yet uncommitable objects. The impact of this on recovery is also discussed.
A system is presented for 'programming in the many' that adapts language-based editors for individual programmers to support the automatic checking of semantic interdependencies among modules as they are devel...
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ISBN:
(纸本)0818607378
A system is presented for 'programming in the many' that adapts language-based editors for individual programmers to support the automatic checking of semantic interdependencies among modules as they are developed in parallel by multiple programmers on a collection of workstations distributed across a local area network. The focus is on the reliability of these distributed programming environments as some modules become inaccessible and later return to availability. The primary contributions are the decentralized control of the programming environment, firewalls, a mechanism that encapsulates individual modules to protect them from external failures, and a special network layer that enables the system to be highly available and reliable in the face of an unreliable network. The firewalls and network layer together support reestablishment of consistency among fully replicated data in the context of distributed programming environments.
作者：
Banatre, J.P.Banatre, M.Ployette, F.INSA
Inst de Recherche en Informatique et Systemes Aleatoires Rennes Fr INSA Inst de Recherche en Informatique et Systemes Aleatoires Rennes Fr
The first part of this paper describes a distributed auction bidding system and its major requirements. The hardware and software structure of the system are quickly sketched. The second part of the paper concentrates...
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ISBN:
(纸本)0818605014
The first part of this paper describes a distributed auction bidding system and its major requirements. The hardware and software structure of the system are quickly sketched. The second part of the paper concentrates upon crash recovery aspects in the system. The three major aspects which are developed concern: (i) stable storage, (ii) implementation of commit protocol and (iii) description of recovery algorithms.
作者：
Minoura, ToshimiUniv of Southern California
Dep of Electrical Engineering-Systems Los Angeles CA USA Univ of Southern California Dep of Electrical Engineering-Systems Los Angeles CA USA
Two schemes for realizing mutual exclusion in a distributed system are discussed. The ranking scheme is a common framework for the three mutual exclusion algorithms found in the literature. In the ranking scheme, the ...
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Two schemes for realizing mutual exclusion in a distributed system are discussed. The ranking scheme is a common framework for the three mutual exclusion algorithms found in the literature. In the ranking scheme, the site with the smallest rank number can enter the mutual exclusion state. Another method of realizing mutual exclusion is to let a single 'control token' float in the system and to allow only its holder to enter the mutual exclusion state. One result in this paper shows how the control token is effectively transferred by the ranking scheme.
作者：
York, GaryCarnegie-Mellon Univ
Dep of Electrical Engineering Pittsburgh PA USA Carnegie-Mellon Univ Dep of Electrical Engineering Pittsburgh PA USA
Many modern reliable systems.are N-modular redundancy and voting to achieve the required reliability. Most of these systems.assume that the redundant modules are synchronized. Experiments have been performed on the mu...
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ISBN:
(纸本)0818605014
Many modern reliable systems.are N-modular redundancy and voting to achieve the required reliability. Most of these systems.assume that the redundant modules are synchronized. Experiments have been performed on the multiprocessor with redundant software modules that are allowed to execute with various degrees of asynchrony. The performance of such systems.has been experimentally determined along two lines. The first experiment determined how much overhead is added to the system execution time as the voting frequency changes. The second experiment shows how much asynchrony can be tolerated in prcess execution for three different experimental paradigms. Mathematical models for the experiments have been developed that closely model the experimental results.
Intuition tells us that in a distributed DBMS using two phase locking, the ratio (denoted by R/W) of read-only to update transactions affects system performance - the higher the ratio, the better the performance. Read...
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Intuition tells us that in a distributed DBMS using two phase locking, the ratio (denoted by R/W) of read-only to update transactions affects system performance - the higher the ratio, the better the performance. Read-only transactions only request share locks, and thus should cause fewer conflicts and deadlocks among all transactions. Therefore both read-only and update transactions are expected to perform better if R/W is higher. The results of a study contradicting this intuition are reported, and the relationship between the R/W ratio and system performance in detail.
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.
Adaptability is an essential tool for managing escalating software costs and to build high-reliability, high-performance systems. Algorithmic adaptability, which supports techniques for switching between classes of sc...
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Adaptability is an essential tool for managing escalating software costs and to build high-reliability, high-performance systems. Algorithmic adaptability, which supports techniques for switching between classes of schedulers in distributed transaction systems. is modeled. RAID, an experimental system implemented to support experimentation in adaptability, is discussed. Adaptability features in RAID, including algorithmic adaptability, fault tolerance, and implementation techniques for an adaptable server-based design, are modeled.
A nested transactions mechanism called the Eden Resource Management System (ERMS) is considered. The key idea in the ERMS design is the hierarchical composition of transaction managers. Consequently, at each level of ...
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ISBN:
(纸本)0818607378
A nested transactions mechanism called the Eden Resource Management System (ERMS) is considered. The key idea in the ERMS design is the hierarchical composition of transaction managers. Consequently, at each level of nesting ERMS uses well-known concurrency control and crash recovery mechanisms of single-level transaction systems. Resources controlled by ERMS can be general objects of any type;their distribution, location, and replication are transparent to the client. For multiple resources, ERMS provides nested synchronization to increase parallelism and multilevel failure isolation to facilitate crash recovery. Uniform syntax for top-level and subtraction allows safe and easy composition of transactions. An example taken from a demonstration application illustrates the use of ERMS and its typical actions.
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