Deadlock detection and resolution is one of the major component of a successful distributed database management system. In this paper, we discuss deadlock detection and resolution strategies and present two approaches for detecting and resolving deadlocks in both general distributed database systems and in distributed real-time database systems. Our first approach is to collect information on connectivity of nodes of the overall Transaction Wait-For Graph (TWFG) of the distributed database system and then use these connectivities information to build a local TWFG at each node of the overall TWGF. We then detect the deadlocks by locating the cycles in each local TWFG. To resolve the deadlocks the nodes involved in those cycles in each local TWFG, are removed until there is no cycle in the local TWFGs. Our second approach continuously checks for the occurrences of a deadlock between different transaction trees. As soon as it detects a deadlock it resolves it by aborting one of the transaction tree which has been initiated more recently. Some of the advantages of our approaches over the approaches which are using Probe messages are: (1) no extra storage required to store different probe messages, (2) no false (Phantom) deadlocks are reported, (3) detects and resolve all deadlocks. In addition, our approaches use less messages and time to detect and resolve all deadlocks in the existing TWFG of the distributed database systems.
