5,877 research outputs found
A Concurrency Control Method Based on Commitment Ordering in Mobile Databases
Disconnection of mobile clients from server, in an unclear time and for an
unknown duration, due to mobility of mobile clients, is the most important
challenges for concurrency control in mobile database with client-server model.
Applying pessimistic common classic methods of concurrency control (like 2pl)
in mobile database leads to long duration blocking and increasing waiting time
of transactions. Because of high rate of aborting transactions, optimistic
methods aren`t appropriate in mobile database. In this article, OPCOT
concurrency control algorithm is introduced based on optimistic concurrency
control method. Reducing communications between mobile client and server,
decreasing blocking rate and deadlock of transactions, and increasing
concurrency degree are the most important motivation of using optimistic method
as the basis method of OPCOT algorithm. To reduce abortion rate of
transactions, in execution time of transactions` operators a timestamp is
assigned to them. In other to checking commitment ordering property of
scheduler, the assigned timestamp is used in server on time of commitment. In
this article, serializability of OPCOT algorithm scheduler has been proved by
using serializability graph. Results of evaluating simulation show that OPCOT
algorithm decreases abortion rate and waiting time of transactions in compare
to 2pl and optimistic algorithms.Comment: 15 pages, 13 figures, Journal: International Journal of Database
Management Systems (IJDMS
Internet of Things Cloud: Architecture and Implementation
The Internet of Things (IoT), which enables common objects to be intelligent
and interactive, is considered the next evolution of the Internet. Its
pervasiveness and abilities to collect and analyze data which can be converted
into information have motivated a plethora of IoT applications. For the
successful deployment and management of these applications, cloud computing
techniques are indispensable since they provide high computational capabilities
as well as large storage capacity. This paper aims at providing insights about
the architecture, implementation and performance of the IoT cloud. Several
potential application scenarios of IoT cloud are studied, and an architecture
is discussed regarding the functionality of each component. Moreover, the
implementation details of the IoT cloud are presented along with the services
that it offers. The main contributions of this paper lie in the combination of
the Hypertext Transfer Protocol (HTTP) and Message Queuing Telemetry Transport
(MQTT) servers to offer IoT services in the architecture of the IoT cloud with
various techniques to guarantee high performance. Finally, experimental results
are given in order to demonstrate the service capabilities of the IoT cloud
under certain conditions.Comment: 19pages, 4figures, IEEE Communications Magazin
An Efficient Concurrency Control Technique for Mobile Database Environment
Day by day wireless networking technology and mobile computing devices are becoming more popular for their mobility as well as great functionality Now it is an extremely growing demand to process mobile transactions in mobile databases that allow mobile users to access and operate data anytime and anywhere irrespective of their physical positions Information is shared among multiple clients and can be modified by each client independently However for the assurance of timely access and correct results in concurrent mobile transactions concurrency control techniques CCT happen to be very difficult Due to the properties of Mobile databases e g inadequate bandwidth small processing capability unreliable communication mobility etc existing mobile database CCTs cannot employ effectively With the client-server model applying common classic pessimistic techniques of concurrency control like 2PL in mobile database leads to long duration Blocking and increasing waiting time of transactions Because of high rate of aborting transactions optimistic techniques aren t appropriate in mobile database as well This paper discusses the issues that need to be addressed when designing a CCT technique for Mobile databases analyses the existing scheme of CCT and justify their performance limitations A modified optimistic concurrency control scheme is proposed which is based on the number of data items cached amount of execution time and current load of the database server Experimental results show performance benefits such as increase in average response time and decrease in waiting time of the transaction
To boldly go:an occam-Ļ mission to engineer emergence
Future systems will be too complex to design and implement explicitly. Instead, we will have to learn to engineer complex behaviours indirectly: through the discovery and application of local rules of behaviour, applied to simple process components, from which desired behaviours predictably emerge through dynamic interactions between massive numbers of instances. This paper describes a process-oriented architecture for fine-grained concurrent systems that enables experiments with such indirect engineering. Examples are presented showing the differing complex behaviours that can arise from minor (non-linear) adjustments to low-level parameters, the difficulties in suppressing the emergence of unwanted (bad) behaviour, the unexpected relationships between apparently unrelated physical phenomena (shown up by their separate emergence from the same primordial process swamp) and the ability to explore and engineer completely new physics (such as force fields) by their emergence from low-level process interactions whose mechanisms can only be imagined, but not built, at the current time
Storage Solutions for Big Data Systems: A Qualitative Study and Comparison
Big data systems development is full of challenges in view of the variety of
application areas and domains that this technology promises to serve.
Typically, fundamental design decisions involved in big data systems design
include choosing appropriate storage and computing infrastructures. In this age
of heterogeneous systems that integrate different technologies for optimized
solution to a specific real world problem, big data system are not an exception
to any such rule. As far as the storage aspect of any big data system is
concerned, the primary facet in this regard is a storage infrastructure and
NoSQL seems to be the right technology that fulfills its requirements. However,
every big data application has variable data characteristics and thus, the
corresponding data fits into a different data model. This paper presents
feature and use case analysis and comparison of the four main data models
namely document oriented, key value, graph and wide column. Moreover, a feature
analysis of 80 NoSQL solutions has been provided, elaborating on the criteria
and points that a developer must consider while making a possible choice.
Typically, big data storage needs to communicate with the execution engine and
other processing and visualization technologies to create a comprehensive
solution. This brings forth second facet of big data storage, big data file
formats, into picture. The second half of the research paper compares the
advantages, shortcomings and possible use cases of available big data file
formats for Hadoop, which is the foundation for most big data computing
technologies. Decentralized storage and blockchain are seen as the next
generation of big data storage and its challenges and future prospects have
also been discussed
Review of Some Transaction Models used in Mobile Databases
Mobile computing is presently experiencing a period of unprecedented growth with the convergence of communication and computing capabilities of mobile phones and personal digital assistant. However, mobile computing presents many inherent problems that lead to poor network connectivity. To overcome poor connectivity and reduce cost, mobile clients are forced to operate in disconnected and partially connected modes. One of the main goals of mobile data access is to reach the ubiquity inherent to the mobile systems: to access information regardless of time and place. Due to mobile systems restrictions such as, for instance, limited memory and narrow bandwidth, it is only natural that researchers expend efforts to soothe such issues. This work approaches the issues regarding the cache management in mobile databases, with emphasis in techniques to reduce cache faults while the mobile device is either connected, or with a narrow bandwidth, or disconnected at all. Thus, it is expected improve data availability while a disconnection. Here in the paper, we try to describe various mobile transaction models, focusing on versatile data sharing mechanisms in volatile mobile environments
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