Deadlock detection and resolution in distributed processing systems (ddbms, synchronization)

The availability of distributed databases is directly affected by the timely detection and resolution of deadlocks. Consequently, mechanisms are needed to make deadlock detection algorithms resilient to failures. Presented first in this dissertation is a centralized algorithm that allows transactions to have multiple requests outstanding. Next, a new distributed deadlock detection algorithm (DDDA) is presented, using a global detector (GD) to detect global deadlocks and local detectors (LDs) to detect local deadlocks. This algorithm essentially identifies transaction-resource interactions that may cause global (multisite) deadlocks. Such interactions are reported to the global controller, while the remaining interactions are handled locally. In order to make the DDDA fault-tolerant, three procedures have been incorporated to handle failures of the controller, failures of any of the local sites, and failures of communication links. This enhanced algorithm, called FTDDDA, improves the overall performance of the database system by improving resiliency of the deadlock detection service.