Abstract: In a distributed network of processors, a method for completing update transactions using update transaction timers after failure of one processor. Failed slave processors are updated with other slave processors using a record of the last completed database update transaction at each processor prior to failure and using a journal in the master processor that records steps of database update transactions generated by the master database processor.

Abstract: A diagnostic and parity generation arrangement is disclosed for use with a pair of duplicated processing units operating in synchronism. A distinct parity generator is associated with the "output bus" of each processor for indicating the parity of the information thereon. When a peripheral address register is loaded, the parity indications generated by the parity generators are compared to ensure that identical information is being applied to the output buses; and when information is written in memory, these same parity indications are combined to generate parity information over the data to be stored and over the address at which the data and the generated parity information are stored. These same parity indications are also utilized during read operations to generate another parity indication which is compared with a retrieved parity indication.