Increased data reliability, faster localized access to data, and the potential for upward scaling of data capacity are advantages to distributing data in a network or decentralized computer systems. One problem in a ...
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Increased data reliability, faster localized access to data, and the potential for upward scaling of data capacity are advantages to distributing data in a network or decentralized computer systems. One problem in a distributed system, however, is the efficient processing of queries. database management systems must consider that the transmission of data over communication lines introduces substantial time delays and that distributedsystems process and transmit data in parallel at separate points in the network. A distribution strategy for a query is the arrangement of data processing and data transmissions. Optimization algorithms that will derive optimal distribution strategies with minimal response time and minimal total time can be designed for simple queries. These algorithms are used as a basis for developing a general query processing algorithm and the query optimization algorithm can be integrated into the design of a distributed management system. Formulas. Flow charts.
This paper presents a novel scheme for implementing the flexible replica control protocol[13] in the distributed database systems. The scheme requires less nodes to be locked to perform the read(write) operations. Thi...
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This paper presents a novel scheme for implementing the flexible replica control protocol[13] in the distributed database systems. The scheme requires less nodes to be locked to perform the read(write) operations. This not only provides better performance, but also provides the system designer extra flexibility to implement the protocol.
Scheduling transactions in advanced applications of distributed database systems, such as real-time distributed groupware systems and network management systems, are different from that in traditional databasesystems...
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Scheduling transactions in advanced applications of distributed database systems, such as real-time distributed groupware systems and network management systems, are different from that in traditional databasesystems. In this paper, we propose new scheduling models, LWL for coordinating cooperative activities in real-time distributed groupware systems, and GTM for providing interoperability to network management systems, respectively.
Advanced software application systems commonly execute atop multiple interconnected computing platforms. Regardless of whether the underlying platforms being homogeneous or heterogeneous, such systems require basic re...
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This paper attempts a comprehensive study of deadlock detection in distributed database systems. First, the two predominant deadlock models in these systems and the four different distributed deadlock detection approa...
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This paper attempts a comprehensive study of deadlock detection in distributed database systems. First, the two predominant deadlock models in these systems and the four different distributed deadlock detection approaches are discussed. Afterwards, a new deadlock detection algorithm is presented. The algorithm is based on dynamically creating deadlock detection agents (DDAs), each being responsible for detecting deadlocks in one connected component of the global wait-for-graph (WFG). The DDA scheme is a "self-tuning" system: after an initial warm-up phase, dedicated DDAs will be formed for "centers of locality", i.e., parts of the system where many conflicts occur. A dynamic shift in locality of the distributed system will be responded to by automatically creating new DDAs while the obsolete ones terminate. In this paper, we also compare the most competitive representative of each class of algorithms suitable for distributed database systems based on a simulation model, and point out their relative strengths and weaknesses. The extensive experiments we carried out indicate that our newly proposed deadlock detection algorithm outperforms the other algorithms in the vast majority of configurations and workloads and, in contrast to all other algorithms, is very robust with respect to differing load and access profiles.
Data allocation problem (DAP) in distributed database systems is a NP-hard optimization problem with significant importance in parallel processing environments. The solution of problem aims to minimize the total cost ...
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Data allocation problem (DAP) in distributed database systems is a NP-hard optimization problem with significant importance in parallel processing environments. The solution of problem aims to minimize the total cost of transactions and settlement of queries in which he main cost regards to the data transmission through the distributed system. These costs are affected by the strategy how to allocate fragments to the sites. Researchers have been solving this challenging problem by applying soft computing methods especially evolutionary algorithms. This study proposes a novel hybrid method based on differential evolution (DE) algorithm and variable neighborhood search (VNS) mechanism for solving DAP problem. The suggested hybrid method (DEVNS) aims to increase the performance of DE algorithm by applying effective selection and crossover operators. Moreover, DEVNS goals to improve the solutions found so far using VNS technique. By applying VNS, more promising parts of search space can be extracted. Eventually, the introduced DEVNS explores the search space via DE and fulfills more exploitation by neighborhood search mechanism. Performance of proposed DEVNS is experimentally evaluated against nine state-of-the-art methods using well-known benchmarks reported in literature. Obtained results exhibits that proposed DEVNS takes the first position for 13 of 20 test problems. Likewise, Friedman aligned rank test is carried out to demonstrate that there is significant statistical difference between all methods.
Broadcast local area networks are being widely deployed in organizations for their interconnectivity. Also, computer workstations are increasingly becoming more sophisticated in their ability to store and process data...
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Broadcast local area networks are being widely deployed in organizations for their interconnectivity. Also, computer workstations are increasingly becoming more sophisticated in their ability to store and process data. Thus, advanced information systems are being constructed, using databases whose component relational tables are distributed over multiple computer nodes connected through a local area network. In this paper, we present an efficient query optimization algorithm for processing queries expressed on tables distributed over a broadcast local area network. The algorithm is analyzed and compared with the query optimization algorithm proposed by Hevner et al. called BN_General, for databases distributed over the broadcast-based local area network. We show that the proposed algorithm offers better performance. An example to illustrate the working of this algorithm is provided.
The problem of optimal query processing in distributed database systems was shown to be NP-hard. This means that heuristic algorithms are necessary to solve the query processing problem. In this paper, we describe alg...
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The problem of optimal query processing in distributed database systems was shown to be NP-hard. This means that heuristic algorithms are necessary to solve the query processing problem. In this paper, we describe algorithms to improve the solutions generated by heuristics. We have identified four properties which optimal semijoin programs for processing tree queries have to satisfy. A semijoin program is represented by an execution graph which specifies the order and the identities of the semijoins to be executed. Given a semijoin program, we can therefore apply these properties to check its optimality. If it does not satisfy these optimality properties, the associated improvement algorithms can be applied to improve this program. No assumptions have been made about the relation size and the selectivity of the semijoins.
A model is developed for allocating tables in a distributeddatabase system. The model considers memory cost, transmission cost, table size and request rates, as well as updating rates of tables, the maximum allowable...
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A model is developed for allocating tables in a distributeddatabase system. The model considers memory cost, transmission cost, table size and request rates, as well as updating rates of tables, the maximum allowable expected access times to tables at each computer and the memory capacity of each computer. The objective function is concerned with overall operating cost optimality. In this regard, the model is formulated as a non-linear integer zero-one programming problem, which can be converted into a linear zero-one programming model.
This paper investigates the problem of allocating relational database fragments to a network to minimize the overall communication cost for processing a given set of transactions. This problem is known as NP-hard. In ...
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This paper investigates the problem of allocating relational database fragments to a network to minimize the overall communication cost for processing a given set of transactions. This problem is known as NP-hard. In this paper, we transfer the optimal data allocation problem to an integer linear program subject to various constraints, such as network load capacity and storage capacity of each individual computer. Using the presented transformation, we suggest the application of integer linear programming algorithms (fast in practice) to approach the optimal data allocation problem.
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