An Adaptive Context-Aware Transaction Model for Mobile and Ubiquitous Computing

Transaction management for mobile and ubiquitous computing (MUC)aims at providing mobile users with reliable and transparent services anytime anywhere. Traditional mobile transaction models built on client-proxy-server architecture cannot make this vision a reality because (1) in these models, base stations (proxy) are the prerequisite for mobile hosts (client) to connect with databases (server), and 2)few models consider context-based transaction management. In this paper, we propose a new network architecture for MUC transactions, with the goal that people can get online network access and transaction even while moving around; and design a context-aware transaction model and a context-driven coordination algorithm adaptive to dynamically changing MUC transaction context. The simulation results have demonstrated that our model and algorithm can significantly improve the successful ratio of MUC transactions

A model for transaction management in mobile databases

The evolution of mobile computing devices and wireless networks has created a new mobile computing environment. Users equipped with a mobile host can access, retrieve, and process information while in mobility. Laptops become more powerful data processing elements. Traditional transaction model has moved forwarding to mobile transaction. This paper proposed the model with the aims at solving the stated issues. A key requirement in such an environment is to support frequent disconnection of mobile database. Transaction management models for databases, in particular the centralized databases, has long been established. Due to the nature of mobile computers, the traditional transaction management models are no longer appropriate. This paper present a model that implements this framework in an asynchronous and synchronous system

Transaction Management Model for Mobile Database

Transaction support is crucial in mobile data management. Specific characteristics of mobile environments (e.g. variable bandwidth, disconnections, and limited resources on mobile hosts) make traditional transaction management techniques no longer appropriate. This is due the fact that the Atomicity, Consistency, Isolation and Durability (ACID) properties of transactions are not simply followed, in particular the consistency property. Thus, transaction management models adopting weaker form of consistency are needed and these models can now tolerate a limited amount of consistency. As a result, several transaction management models for mobile databases have been proposed, each of which has attempted to overcome some issues pertaining to transaction processing in mobile environment. However, issues such as (a) only one mobile host (MH) is allowed to update the data item (b) large number of rejected transactions (c) commit time execution of transactions at mobile host (MH) is large are not well handled. The proposed the model with the aims at solving the stated issues. The main idea underlying the model is that transaction execution can be done at the base station (BS) and mobile host (MHs). Transactions at a MH can update data locally and then precommit. When the MH connects to the BS, these pre-committed transactions are sent to the BS and re-executed as base transactions (BT) to maintain data consistency at the BS. BTs are serialized on the master data stored at the BS. This will results in data consistency. The availability of data item at MHs makes the execution of transaction at MHs possible. Each MH is allocated some value of data item, and the rest of it is kept at the base server. By having the own this resource, a transaction at a MH is allowed to update the data item within the limit of iSi. The model has been implemented and the result has shown that the model works correctly as expected

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

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

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