We propose a new methodology for the optimization of the query processing in relational and table database networks, and its theoretical foundations. As optimization criteria, we apply the anticipated cost and time of...
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ISBN:
(纸本)0852966210
We propose a new methodology for the optimization of the query processing in relational and table database networks, and its theoretical foundations. As optimization criteria, we apply the anticipated cost and time of search, as well as the amount of information retrieved. The latter criterion is based on the notion of relative information contents which we introduce here for the relational and table databases. We formulate the multicriteria optimization problem and derive the optimal sequence of retrieving information from different databases. Optimal search strategies so derived may be regarded as Markov decision trees. The query processing system is supplemented by a learning scheme allowing to update ex post the knowledge base characterizing the information contents of each database in the network. Finally, a practical implementation of the above system is discussed.
In a distributeddatabase system (DDBS), the users and the copies of the data items are distributed over the nodes of a computer network. The design of such a system requires precise concepts for the correct concurren...
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ISBN:
(纸本)078034054X
In a distributeddatabase system (DDBS), the users and the copies of the data items are distributed over the nodes of a computer network. The design of such a system requires precise concepts for the correct concurrent processing of user transactions, for the data access concurrency control (CC) and for the representation and manipulation of data. We model a generic DDBS as a parameterized formal executable high-level Petri net whose database is specified as Abstract Data Types (ADT). A particular DDBS is generated by initial declarations (for the configuration of the network and the distribution of users and data items over its nodes) and parameters (for the chosen CC method and data types). The correctness of the model can be verified rigorously by means of formal analysis methods and by inspecting the occurrence graph. The model constitutes a (rapid) prototype whose simulation can demonstrate the functionality to the designers and the man/machine interface to prospective users. Moreover, the execution of the model allows to derive performance figures for particular applications that can be used for tuning.
We address the two-stage multi-machine assembly scheduling problem to minimize mean completion times of all jobs. This problem has many applications in practice including the queries scheduling on distributeddatabase...
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ISBN:
(纸本)9781880843864
We address the two-stage multi-machine assembly scheduling problem to minimize mean completion times of all jobs. This problem has many applications in practice including the queries scheduling on distributed database systems This problem has been recently addressed in the literature for which an efficient heuristic, called SAK, was developed for the case when m=2. In this paper, we address the problem for the case m=2. We propose a hybrid tabu search (HTS) heuristic and show that the overall average error of SAK is more than twice that of HTS while the average CPU time of SAK is five times that of HTS. This clearly indicates that the heuristic HTS is much better than the only existing heuristic available for the problem, i.e., SAK.
In order to store and process data at large-scale, distributeddatabases are built to partition data and process it in parallel on distributed nodes in a cluster. When the database concurrently execute heterogeneous q...
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The resiliency of distributed database systems can be realized through a collection of integrated fault-tolerance mechanisms. These include data replication techniques, failure detection, failure isolation through rec...
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ISBN:
(纸本)0897916263
The resiliency of distributed database systems can be realized through a collection of integrated fault-tolerance mechanisms. These include data replication techniques, failure detection, failure isolation through reconfiguration and adaptability, and non-blocking atomic commitment. Collectively, these mechanisms enhance the availability and operability of the system in the presence of various types of site and communication failures. In this paper, we focus on mechanisms for data replication, failure detection, and reconfiguration. We present the implementation details of each of these mechanisms along with their integration within the RAID system developed at Purdue. Data replication is implemented through the partial replication of data relations, and through the use of a library of replication control methods. An on-line replication control server (RC) provides highly available database operations through the adaptable use of these methods. Failure detection is implemented via a reliable surveillance facility that monitors the changes in system connectivity. Such failures include site and communication failures as well as network partition. Repairs and network merges are also detected by this facility, thus leading to the automatic initiation of recovery. We will show how failure isolation is achieved through data and server reconfiguration and by the adaptable use of replication methods.
The main issues in processing read-only transactions (ROTs) are correctness, data currency and performance. The popular two-phase locking (2PL) protocol processes the transactions correctly according to serializabilit...
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Recently with the advent of IT and the wide spread use of the Internet, new user oriented production and logistic systems, such as the supply chain management system, have been required in order to cope with the drast...
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Allocating data fragments in distributed database systems is an important issue in distributeddatabase (DDB) systems. In this research work, we will show how rule based policy languages can be used to represent diffe...
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Allocating data fragments in distributed database systems is an important issue in distributeddatabase (DDB) systems. In this research work, we will show how rule based policy languages can be used to represent different data fragment allocation techniques. Results indicate that, using rule based languages like prolog can significantly simplify the representation of such algorithms for any further developments and optimizations. Our examples show that our approach can be extended to be used in different areas of distributedsystems.
In this paper, a centralized deadlock detection algorithm with multiple outstanding requests (CDDMOR) is proposed for use in distributed database systems and transaction-processing systems. This algorithm allows a pro...
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An adaptive concurrency control protocol is proposed for distributed database systems where data and resource contention have adverse effects on performability. The protocol dynamically switches between two existing c...
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An adaptive concurrency control protocol is proposed for distributed database systems where data and resource contention have adverse effects on performability. The protocol dynamically switches between two existing concurrency control mechanisms, namely, an optimistic one called the 'exclusive writer with locking option' and a pessimistic one referred to as 'primary site locking.' Adaptation is based on partial knowledge about the system that is available locally at any database site such that no overhead (no additional inter-database site message exchange for collecting information) is incurred. The evaluation results indicate a potential for significant gains in performability from the use of adaptive concurrency control techniques.
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