Abstract: In a fault-tolerant system employing software fault-tolerance techniques, the identifiers used for control blocks or objects referenced on an interface between two co-operating partner software processes either require resynchronization after fail over of one or both of the partners or impose unwanted performance impacts on normal operation of the system. Replicated handles enhance the techniques currently used in such systems to avoid both the need for resynchronization and other potential performance impacts of the prior art.

Abstract: When updating a running program in a system that uses a one-to-one backup program, fault-tolerance is lost while the backup program is itself being updated. To overcome this temporary loss of an available backup program, the number of backup copies of a software process is temporarily and dynamically increased during the software upgrade. The extra backup software processes may run on an unused processing unit or may run as an extra software process on a processing unit which is already performing a task. The technique may be applied to communication line cards.