Concurrent data access in mobile heterogeneous systems

Abstract

A mobile computing environment involves accessing information through a wireless network connection. The mobile unit may be stationary, in motion, and/or intermittently connected to a fixed (wired) network. As technology advances are made in software and hardware, the feasibility of accessing information "anytime, anywhere" is becoming a reality.There are similarities involved in accessing information in a multidatabase environment and mobile computing environment. We propose to superimpose a wireless-mobile computing environment on a multidatabase system to realize a system capable of effectively accessing a large amount of data over a wireless medium (MDAS -Mobile Data Access System). We show how one can easily map solutions from one environment to another.As a potentially large number of users may simultaneously access the available data, there are several issues involved in the ability to concurrently manage transactions. Current concurrency control schemes do not efficiently manage these accesses because they do not address the limited bandwidth and frequent disconnections associated with wireless networks. This paper proposes a new hierarchical concurrency control algorithm. The proposed concurrency control algorithm uses global locking tables created with semantic information contained within the hierarchy. The performance of the new algorithm is simulated and the results are presented.

A Transaction Processing Model for the Mobile Data Access System

“…The model is built on the concept of global transactions in multidatabase based on the Summary Schemas Model [6]. This work expands our effort reported in [13] by implementing an additional layer on top of the MDBS that handles mobile transactions, disconnection, and long-lived transaction.…”

“…The system parameters were derived from the underlying platform. Additional parameters for the mobile component of the system were obtained from the work reported in [13]. These parameters are presented in Tables 1-3.…”

“…The mobile computing environment is a collection of mobile hosts (MH) and a fixed networking system [8], [10], [13]. The fixed networking system consists of a collection of fixed hosts connected through a wired network.…”

“…Temporary disconnection should be tolerated with a minimum disruption of transaction processing, and suspension of transactions on either stationary or mobile hosts. In order for users to work effectively during periods of disconnection, mobile computers will require a substantial degree of autonomy [1], [13], [18]. Effects of mobile transactions committed during disconnection should be incorporated into the database while guaranteeing data and transaction correctness upon reconnection [18].…”

“…To support mobile users, it is necessary to augment the existing multidatabases with wireless networking capabilities. This augmented multidatabase is known as a Mobile Data Access System (MDAS) [13].…”