MEYHOD AND APPARATUS FOR INTER-NODE DEADLOCK AVOIDANCE ON A PARALLEL PROCESSING SYSTEM

The invention provides a method and apparatus including a programming product fo r a parallel data processing system having a plurality of nodes interconnected by communication paths, in which one or more sets of data present at one or more so urce nodes of the system is required to be sent on a plurality of communication paths having communication buffers to selected nodes of the database system for processing, a system of communicating the data over the paths between the nodes to avoid deadlocking the processing system, including: accessing data from the one or more source nodes i n subsets of the data; sending the subsets of data on a plurality of paths to the selected nodes of the processing system; if a path of the paths intended for the sending of one or more of the subsets of data becomes blocked, suspending the sending of subsets o f the data on the path for a predetermined time period; if the blocked path becomes ca pable of accepting additional data before the predetermined time period has expired, resu ming the sending of subsets of data on the path; however, if the predetermined time perio d expires without the path becoming available, placing one or more subsequent subsets of d ata intended for the path into an overflow buffer; when the blocked path again becom es free, sending the subsets of data from the overflow buffer on the path to the intended recipient node for processing.