Data Replication can be used to improve data availability in distributeddatabase environments. In such a system, a mechanism is required to maintain the consistency of the replicated data. Grid structure technique ba...
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Majority of the research in multilevel secure database management systems (MLS/DBMS) focuses primarily on centralized databasesystems. However, with the demand for higher performance and higher availability, database...
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ISBN:
(纸本)9728865198
Majority of the research in multilevel secure database management systems (MLS/DBMS) focuses primarily on centralized databasesystems. However, with the demand for higher performance and higher availability, databasesystems have moved from centralized to distributed architectures, and the research in multilevel secure distributeddatabase management systems (MLS/DDBMS) is gaining more and more prominence. Concurrency control is an integral part of databasesystems. Secure concurrency control algorithms proposed in literature achieve correctness and security at the cost of declined performance of high security level transactions. These algorithms infringe the fairness in processing transactions at different security levels. Though the performance of different concurrency control algorithms have been explored extensively for centralized multilevel secure database management systems but to the best of author's knowledge the relative performance of transactions at different security levels using secure concurrency control algorithm for MLS/DDBMS has not been reported yet. To fill this gap, this paper presents a detailed simulation model of a distributeddatabase system and investigates the performance price paid for maintaining security with concurrency control in a distributeddatabase system. The paper investigates the relative performance of transactions at different security levels.
In distributed database systems, as cluster scales grow, efficiency and availability become critical considerations. In a cluster, a common approach to high availability is using replication, but this is inefficient d...
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In distributed database systems, as cluster scales grow, efficiency and availability become critical considerations. In a cluster, a common approach to high availability is using replication, but this is inefficient due to its low storage utilization. Erasure coding can provide data reliability while ensuring high storage utilization. However, due to the large number of coding and decoding operations required by the CPU, it is not suitable for some frequently updated data. In order to optimize the storage efficiency of the data in the distributed system without affecting the availability of the data, this paper proposes a data temperature recognition algorithm that can distinguish data tablets and divides data tablets into three types, cold, warm, and hot, according to the frequency of access. Combining three replicas and erasure coding technology, ER-store is proposed, a hybrid storage mechanism for different data types. At the same time, we combined the read-write separation architecture of the distributeddatabase system to design the data temperature conversion cycle, which reduces the computational overhead caused by frequent updates of erasure coding technology. We have implemented this design on the CBase database system based on the read-write separation architecture, and the experimental results show that it can save 14.6%-18.3% of the storage space while meeting the efficient access performance of the system.
While networking technology provides physical connectivity for the heterogeneous and distributeddatabases, the logical connectivity of such databases can be accomplished only when the heterogenetites of the objects s...
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While networking technology provides physical connectivity for the heterogeneous and distributeddatabases, the logical connectivity of such databases can be accomplished only when the heterogenetites of the objects stored in these diverse databases are resolved. However, this is still yet a major challenge that remains to be realized. In this paper, we develop a reactive multidatabase architecture that emphasizes the dynamic interactions between the local and global systems to maintain object consistency between local databases and object relativism between local and global systems so as to support the interoperability of the heterogeneous databases over time. In particular, we incorporate the Event-Condition-Action (E-C-A) rules into the architecture to provide a suitable platform for specification of global reactions to the anticipated changes of the local databases, as well as of the global users. Such rules extend the power of multidatabasesystems to deal with observation of the objects and events and thus allow the explicit specification, recognition and resolution of the temporal conditions and changes. Our targeted application domains include geographic information system (GIS), scientific database system and digital libraries.
Realization of modern database management systems requires extensions to conventional query processing techniques, namely, it requires support for multiquery processing. In this paper, we briefly outline the areas in ...
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Realization of modern database management systems requires extensions to conventional query processing techniques, namely, it requires support for multiquery processing. In this paper, we briefly outline the areas in which we perceive the greatest need for multiquery optimization research. Also, we propose a new multiquery approach to the optimization of distributed query processing. The proposed multiquery processing approach eliminates redundant execution of sharable operations, thus improving not only the individual query response time but also the total system throughput. Consequently, system utilization is enhanced.
This paper presents an idea for accommodating mixed workloads, OLAP and OLTP on the same table without actually replicating the data into separate table. The method presented in this paper allows the user to define mu...
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This paper presents an idea for accommodating mixed workloads, OLAP and OLTP on the same table without actually replicating the data into separate table. The method presented in this paper allows the user to define multiple logical views of the table to applications having different needs on the amount of data. This is achieved by selectively hiding partitions from applications through selective transformation of the metadata seen by applications. Since the abstraction happens at metadata level with in the database, applications can benefit from partition hiding almost transparently. The proposed solution will reduce I/O operations and hence will improve overall query performance. This technique is in contrast to views which lack the ability to incorporate semantic information in them.
This paper presents a new atomic commitment protocol, enhanced three phase commit (E3PC),that always allows a quorum in the system to make progress. Previously suggested quorum-based protocols (e.g., the quorum-based ...
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This paper presents a new atomic commitment protocol, enhanced three phase commit (E3PC),that always allows a quorum in the system to make progress. Previously suggested quorum-based protocols (e.g., the quorum-based three phase commit (3PC) (Skeen, 1982)), allow a quorum to make progress in case of one failure. If failures cascade, however, and the quorum in the system is "lost" (i.e., at a given rime no quorum component exists), a quorum can later become connected and still remain blocked. With our protocol, a connected quorum never blocks. E3PC is based on the quorum-based 3PC (Skeen. 1982), and it does not require more time or communication than 3PC. We describe how this protocol can be exploited in a replicated database setting, making the database always available to a majority of the sites. (C) 1998 Academic Press.
Proposes a new methodology for the optimization of the query processing in relational and table database networks, and its theoretical foundations. As optimization criteria, the author applies the anticipated cost and...
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Proposes a new methodology for the optimization of the query processing in relational and table database networks, and its theoretical foundations. As optimization criteria, the author applies 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 the author introduces here for relational and table databases. The author formulates the multicriteria optimization problem and derives 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 one 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.< >
One of the most critical aspects of distributeddatabase design and management is fragmentation. If the fragmentation is done properly, we can expect to achieve better throughput from such systems. The primary concern...
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A major cost in retrieving multimedia data from multiple sites is the cost incurred in transferring multimedia data objects (MDO's) from different sites to the site where the query is initiated. The objective of a...
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A major cost in retrieving multimedia data from multiple sites is the cost incurred in transferring multimedia data objects (MDO's) from different sites to the site where the query is initiated. The objective of a data allocation algorithm is to locate the MDO's at different sites so as to minimize the total data transfer cost incurred in executing a given set of queries, There is a mutual dependency between data allocation and query execution strategies in that the optimal allocation of MDO's depends on the query execution strategy employed by a distributed multimedia system while the query execution strategy optimizes a query based on this allocation, In this paper, we flu the query execution strategy and develop a site-independent MDO dependency graph representation to model the dependencies among the MDO's accessed by a query, Given the MDO dependency graphs as well as the set of multimedia database sites, data transfer costs between the sites, the allocation limit on the number of MDO's that can be allocated at a site, and the query execution frequencies from the sites, an allocation scheme is generated, We formulate the data allocation problem as an optimization problem, We solve this problem with a number of techniques that broadly belong to three classes: max-flow min-cut, state-space search, and graph partitioning heuristics. The max-flow min-cut technique formulates the data allocation problem as a network-flow problem, and uses a hill-climbing approach to try to find the optimal solution, For the state-space search approach, the problem is solved using a best-first search algorithm, The graph partitioning approach uses two clustering heuristics, the agglomerative clustering and divisive clustering, We evaluate and compare these approaches, and assess their cost-performance trade-offs, All algorithms are also compared with optimal solutions obtained through exhaustive search, Conclusions are also made on the suitability of these approaches to different sce
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