The proceedings contains 35 papers. Topics discussed include databases, parallel processing systems, distributed computer systems, data processing, large scale systems, data transfer, data storage, storage allocation,...
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The proceedings contains 35 papers. Topics discussed include databases, parallel processing systems, distributed computer systems, data processing, large scale systems, data transfer, data storage, storage allocation, information management, computer architectures, computer operating systems and data structures.
Economic pressures are dispersing machine intelligence away from centralised computers towards distributed Fieldbus devices. Simultaneously, the control concept is being extended to include other operational factors s...
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ISBN:
(纸本)0780318722
Economic pressures are dispersing machine intelligence away from centralised computers towards distributed Fieldbus devices. Simultaneously, the control concept is being extended to include other operational factors such as quality assurance, process data management, just-in-time maintenance, plant safety and availability. As credible sensing and actuation is an essential pre-requisite for advanced control, validation of the sensor and actuator interface is necessary. As such subsystems are linked to a range of different overall plant systems, we must consider generic validation and its reporting to the 'next level up'. The paper discusses validation features which are best embedded in local devices.
Recent advances in public network technology and emerging database interface standards enable the implementation of a new type of distributed database systems and create demand for improved query distribution and quer...
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Recent advances in public network technology and emerging database interface standards enable the implementation of a new type of distributed database systems and create demand for improved query distribution and query optimization algorithms.
Location management is an important problem in distributed mobile computing. Location management consists of location updates, searches and search-updates. An update occurs when a mobile host changes location. A searc...
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Location management is an important problem in distributed mobile computing. Location management consists of location updates, searches and search-updates. An update occurs when a mobile host changes location. A search occurs when a mobile host needs to be located. A search-update occurs after a successful search. Various strategies can be designed for search, update and search-update. Static location management uses one combination of search, update and search-update strategies throughout the execution. Simulations were carried out to evaluate the performance of different static strategies for various communication and mobility patterns. Simulation results indicate that performing search-updates significantly reduces the message overhead of location management.
The integration of mobile/portable computing devices within existing data networks can be expected to spawn distributed applications that execute on mobile hosts (MHs). For reliability, it is vital that the global sta...
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The integration of mobile/portable computing devices within existing data networks can be expected to spawn distributed applications that execute on mobile hosts (MHs). For reliability, it is vital that the global state of such applications be checkpointed from time to time. A global checkpoint consists of a set of local checkpoints, one per participant. This paper first identifies the problems in recording a consistent global state of mobile distributed applications. The location of a MH within the static network varies with time and therefore, a MH will first need to be located ('searched') in order to obtain its local checkpoint. Moreover, MHs often (voluntarily) disconnect from the network;a disconnected MH is not reachable from the rest of the network. This means that a (disconnected) MH may not be available to provide its local checkpoint. Lastly, a MH is not equipped with stable storage;disk space at a MH is not considered stable due to vulnerability of MHs to loss, theft and physical damage. Therefore, an alternative stable repository is required to save local checkpoints of MHs. This paper presents a checkpointing algorithm for MHs that satisfies these constraints.
We present a scalable garbage collection scheme for systems that store objects at multiple servers while clients run transactions on locally cached copies of objects. It is the first scheme that provides fault toleran...
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We present a scalable garbage collection scheme for systems that store objects at multiple servers while clients run transactions on locally cached copies of objects. It is the first scheme that provides fault tolerance for such a system: Servers recover from failures and retrieve information needed for safe garbage collection;clients do not recover from failures, yet the scheme is able to reclaim objects referenced only from failed clients. The scheme is optimized to reduce overhead on common client operations, and it provides fault tolerance by doing work in the background and during client operations that are infrequent.
Many organisations are now planning to move their operations from total reliance on centralised databases towards distributed environments which may involve the interoperability of a number of heterogeneous databases....
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Many organisations are now planning to move their operations from total reliance on centralised databases towards distributed environments which may involve the interoperability of a number of heterogeneous databases. This study looks at a particular case for an international financial institution, with the likely performance of a proposed globally distributed federated database being compared with the performance of the current centralised system. The performance model developed includes submodels for transaction structure and management, user workload, and distributed heterogeneous databases. Simulations focus on response times for a particular class of credit control/deal entry transactions in the presence of a background load. The results demonstrate that the proposed federated database outperforms the current centralised system, and that this is achievable using currently available technology.
Many applications need transaction-consistent pictures of past states of the database. These applications use the commit time of the transaction to timestamp the data. When a transaction is distributed, the cohorts mu...
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Many applications need transaction-consistent pictures of past states of the database. These applications use the commit time of the transaction to timestamp the data. When a transaction is distributed, the cohorts must vote on a commit time and the coordinator must choose a commit time based on the votes of the cohorts. This implies that timestamps are applied after commit. Until the timestamps are on all the records, one must keep a table of all the committed transaction identifiers and their commit times. The main problem solved is that of determining when all timestamps corresponding to a given transaction have been placed in the records so that a committed transaction entry can be erased from the table. This information must be stable. Logging and recovery details are included.
We propose a new network architecture for personal communication services that provides transparent connectivity to different physical networks and user service customization. User information in this network is manag...
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We propose a new network architecture for personal communication services that provides transparent connectivity to different physical networks and user service customization. User information in this network is managed independently by distributed personal agents(PAs) which are identified by their user's personal ID. PAs interact with each other to establish the best communication paths between their users according to their states.
For a data sharing database system, substantial cost is incurred for global locking, to support both transactions and cache management. Replacing global locks with local locks managed by local lock managers offers the...
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For a data sharing database system, substantial cost is incurred for global locking, to support both transactions and cache management. Replacing global locks with local locks managed by local lock managers offers the opportunity to substantially reduce locking overhead. To do this requires the exploitation of global covering locks. We discuss covering in general, and describe the conflicts required for both covering and intention locks. We then describe how to generate new covering and intention modes when logical and physical resources are equated in a data sharing system, hence reducing locking overhead. The new intention modes, because they conflict, permit cache management without losing fine grained concurrency. Fine grained concurrency with combined resources was not previously possible.
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