Duplicate copies of data at two different locations to detect mutilation. Two-way linked lists. Maintain and check redundant status information. Positive decisions Limited use of GOTOs One entry point per module Check incoming buffered data for mutilation while in buffer. Audits check for resources in an invalid state and restore the resource to a valid state.
Audits try to detect erroneous states before system performance is affected.
Loss of all of a given class of resource may halt call processing. Long loops in programs cause them to consume all of the real time and put the system in overload. Auditing of data resident in more than one processor leads to a race condition. If audits find one error in a data structure then all associated data is assume to be bad. Processes audited by timing, timeout in transient states indicated errors.