Data access

About: Data access is a research topic. Over the lifetime, 13141 publications have been published within this topic receiving 172859 citations. The topic is also known as: Data access.

Transactional computation on clusters

Abstract: Computations are performed on shared datasets in a distributed computing cluster using aggressive speculation and a distributed runtime that executes code transactionally. Speculative transactions are conducted with currently available data on the assumption that no dependencies exist that will render the input data invalid. For those specific instances where this assumption is found to be incorrect—that the input data did indeed have a dependency (thereby impacting the correctness of the speculated transaction)—the speculated transaction is aborted and its results (and all transactions that relied on its results) are rolled-back accordingly for re-computation using updated input data. In operation, shared state data is read and written using only the system's data access API which ensures that computations can be rolled-back when conflicts stemming from later-determined dependencies are detected.

Sundial: harmonizing concurrency control and caching in a distributed OLTP database management system

Abstract: Distributed transactions suffer from poor performance due to two major limiting factors. First, distributed transactions suffer from high latency because each of their accesses to remote data incurs a long network delay. Second, this high latency increases the likelihood of contention among distributed transactions, leading to high abort rates and low performance.We present Sundial, an in-memory distributed optimistic concurrency control protocol that addresses these two limitations. First, to reduce the transaction abort rate, Sundial dynamically determines the logical order among transactions at runtime, based on their data access patterns. Sundial achieves this by applying logical leases to each data element, which allows the database to dynamically calculate a transaction's logical commit timestamp. Second, to reduce the overhead of remote data accesses, Sundial allows the database to cache remote data in a server's local main memory and maintains cache coherence. With logical leases, Sundial integrates concurrency control and cache coherence into a simple unified protocol. We evaluate Sundial against state-of-the-art distributed concurrency control protocols. Sundial outperforms the next-best protocol by up to 57% under high contention. Sundial's caching scheme improves performance by up to 4.6× in workloads with high access skew.

Data access method and data access apparatus for accessing data at on-vehicle information device

Abstract: In a data access method for accessing data in an on-vehicle information device having an on-vehicle memory unit that allows data stored therein to be read out and overwritten by an external apparatus and an on-vehicle control unit that executes a data read and a data overwrite by controlling the on-vehicle memory unit, supplying power to the on-vehicle information device from the external apparatus when a power switch at the on-vehicle information device is in an OFF state, and reading out the data in the on-vehicle memory unit and overwriting the data through control implemented by the external apparatus.

Method and system for protocols for providing voice, data, and multimedia services in a wireless local loop system

Abstract: A method and system for implementing various protocols for a Time Division Duplex (TDD) Code Division Multiple Access (CDMA) wireless local loop system that utilizes unique embedded concentrated access and embedded data access in a Wireless Local Loop (WLL) is described. The method and system further provides for dynamic pool sizing of the access channels. The protocols support POTS (Plain Old Telephone), ISDN, and direct data service in a point to multi-point configuration. The protocols are inherently flexible so as to provide Enhanced Bandwidth and quality of service (QOS) via CDMA. Channel concatenation (multi-code modulation) provides a multiplicity of channels. The system utilizes frequency division duplex (FDD) operation so as to double capacity. The system further utilizes scaleable architecture for bandwidth expansion and higher data rate services.