This research investigates the problem of allocating database fragments across a set of computers connected by a communication network. A mathematical model is presented to aid designers in the development of distribu...
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This research investigates the problem of allocating database fragments across a set of computers connected by a communication network. A mathematical model is presented to aid designers in the development of distributed database systems. The model takes into account the pattern of usage of the databases, communication costs in the network, delays due to queuing of data requests, costs for maintaining consistency among the various copies of a database, and storage costs. A solution procedure based on Lagrangian relaxation is proposed to solve the model. Computational results are reported along with several useful observations. The model is applicable to organizations that are considering migration from a centralized to a distributed computing environment.
This paper describes a system called Trends for managing IT resources in a production server environment. The objective of Trends is to reduce operational costs associated with unplanned outages, unbalanced utilizatio...
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Business Intelligence (BI) is a business management term which refers to applications and technologies which are used together, provide access to and analyze data and information about company operations. Business int...
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Data distribution, data replication and system reliability are key factors in determining the availability measures for transactions in distributed database systems. In order to simplify the evaluation of these measur...
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Data distribution, data replication and system reliability are key factors in determining the availability measures for transactions in distributed database systems. In order to simplify the evaluation of these measures, database designers and researchers tend to make unrealistic assumptions about these factors. In this article, we investigate the effect of such assumptions on the computational complexity and accuracy of such evaluations. We represent a database system with five parameters related to the above factors. Probabilistic analysis is employed to evaluate the availability of read-only and read-write transactions. We consider both the read-one/write-all and the majority-read/majority-write replication control policies. We conclude that transaction availability is more sensitive to variations in degrees of replication, less sensitive to data distribution, and insensitive to reliability variations in a nonhomogeneous system. The computational complexity of the evaluations is found to be mainly determined by the chosen distributeddatabase model, while the accuracy of the results is not so much dependent on the models.
This paper presents an analytical model to allocate files and workload simultaneously among heterogeneous servers that operate distributeddatabases on a two-level local multi-access computer network. The allocation p...
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This paper presents an analytical model to allocate files and workload simultaneously among heterogeneous servers that operate distributeddatabases on a two-level local multi-access computer network. The allocation problem is presented in the form of a non-linear integer programming model. The model incorporates both local processing and data communication overhead. The problem is NP-complete and thus a heuristic is developed. To illustrate its suitability, the heuristic is compared with an exhaustive enumeration method for small problems and with a genetic algorithm for large problems. Computational results imply that the heuristic provide effective database designs. (C) 1997 Elsevier Science Ltd.
This paper describes the status of the pilot system on the distributeddatabase for advanced nuclear materials named Data-Free-Way, Trials of utilization of the system focused on the issues relating to fusion material...
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This paper describes the status of the pilot system on the distributeddatabase for advanced nuclear materials named Data-Free-Way, Trials of utilization of the system focused on the issues relating to fusion materials are mentioned. A relational database management system was utilized to unify useful data of material properties into the distributeddatabase. The other software such as operating system, network utilities, etc. were also incorporated. To make retrieval rationally and promptly, a menu for selecting data items was expanded for the system. High-temperature tensile properties of type 316 stainless steel irradiated in various reactors were analyzed. The results indicated that correlation between postirradiation total elongation versus amounts of displacement damage was better than that between postirradiation total elongation versus helium accumulation in the alloys. Furthermore, correlation coefficients of the data between those two variables were better at higher temperature ranges.
When constructing a large-scale database system, data replication is useful to give users efficient access to that data. However, for databases with a very large number of replica sites, using traditional networking c...
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When constructing a large-scale database system, data replication is useful to give users efficient access to that data. However, for databases with a very large number of replica sites, using traditional networking concurrency control protocols makes communication too costly for practical use. In this paper, we propose a new protocol called ECHO for concurrency control of replica data distributed on a large scale. Using broadcasting, such as satellite broadcasting, terrestrial broadcasting, and cable television, the ECHO method can keep communication costs constant, regardless of the number of sites. The ECHO method also has a backup mechanism for failed broadcast reception using the communication network.
Using a distributeddatabase system as a part of the distributed web server architecture has obvious advantages. It is shown that a first phase distributeddatabase system can be build by extending an existing object ...
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Using a distributeddatabase system as a part of the distributed web server architecture has obvious advantages. It is shown that a first phase distributeddatabase system can be build by extending an existing object oriented database system with application-specific additions. A web database is implemented, as a part of the traditional HTTP-based distributed web server, using this distributeddatabase system.
Purpose - Damage assessment and recovery play key roles in the process of secure and reliable computer systems development. Post-attack assessment in a distributeddatabase system is rather complicated due to the indi...
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The design of distributeddatabase (DDBs) destined to store user information is a key issue in third-generation mobile communication systems such as UMTS. In particular, the problem of determining the most appropriate...
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The design of distributeddatabase (DDBs) destined to store user information is a key issue in third-generation mobile communication systems such as UMTS. In particular, the problem of determining the most appropriate DDB architectures for UMTS is critical due to the anticipated requirements of high distribution and adaptability of information. This paper presents a model which allows different DDB architectures to be evaluated, in terms of query loads and average search times. The model proposed puts no constraints on either the DDB structure arrangement or the user position characterization. The paper also discusses a real, significant case study, concerning a query operation arising from an access procedure performed on the DDB of a communication network covering an urban area.
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