Transaction management in mobile multidatabases.

Abstract

This dissertation studies transaction management in the mobile Multidatabase environment. That is, it studies the management of transactions within the context of the mobile and Multidatabase environments. Two new transaction management techniques for the mobile Multidatabase environment i.e., the PS and Semantic-PS techniques are proposed. These techniques define two now states (Disconnected and Suspended) to address the disconnectivity of the mobile user. A new Partial Global Serialization Graph algorithm is introduced to verify the isolation property of global transactions. This algorithm verifies the serializability of a global transaction by constructing a partial global serialization graph. This algorithm relies on the propagation of (serialization) information to ensure that the partial graph contains sufficient information to verify serializability of global transactions. The unfair treatment of mobile transactions due to their prolonged execution time is minimized through pre-serialization. Pre-serialization allows mobile transactions to establish their serialization order prior to completing their execution.

The Internet and advances in wireless communication technology have transformed many facets of the computer environment. Virtual connectivity through the internet has lead to a new genre of software systems, i.e., cooperating autonomous systems---systems that cooperate with each other to provide extended services to the user. Multidatabase systems---a set of databases that cooperate with each other in order to provide a single logical view of the underlying information---is an example of such systems. Advances in wireless communication technology dictate that the services available to the wired user be made available to the mobile user.

Finally, analytical evaluation and simulation is carried out to study the performance of these techniques and to compare their performance to that of the Kangaroo [DHB97] technique. Although the PS and Semantic-PS techniques enforce the isolation property, the evaluation results establish that the service time for these techniques in not significantly greater than that of the Kangaroo technique. In addition, the simulation establishes that pre-serialization effectively minimizes the unfair treatment of mobile transactions.