This is an investigation of issues in debugging distributed programs with large numbers of processes. Existing distributed debugging systems are simple extensions of sequential debugging systems and are inadequate for supporting message-based distributed programs. Distributed programs are inherently different from sequential programs due to the presence of nondeterminism, concurrency and communication delays. The research in distributed debugging supports both state-based and event-based approaches for debugging. The state-based is supported mainly by use of breakpoint predicates detection. A logic for specification of breakpoint predicates characterizes the most useful properties of global traces in a distributed environment. The logic is suitably defined to permit efficient detection of global predicates with out resort to computation of global snapshots. Algorithms have been developed to detect global predicates expressed as simple conjunction, disjunction or sequence of local predicates. These mechanisms can detect a large subset of predicates defined by the logic, even if the predicates are unstable. The main objective is to extend these algorithms for applicability to more general global predicates.
