Abstract: A local computer system has local database, application programs that modify the local database, an a transaction manager that stores audit records in a local audit trail reflecting those application program modifications to the local database. A remotely located computer system has a backup database. A remote data duplication facility (RDF) is partially located in the local computer system and partially in the remote computer for maintaining virtual synchronization of the backup database with the local database. The RDF includes an extractor process executed by said local computer system, and a receiver process and a plurality of updater processes executed by the remote computer system. The extractor process extracts audit records from a local audit trail and transmits those records to the receiver process. The receiver process distributes the audit records into one or more image trail files that are associated with a particular updater process.

Abstract: A computer program measures the execution of machine code instructions in an executing program. A copy of the measured program is made and selected machine instructions are replaced by interrupt-causing breakpoint instructions. As each breakpoint instruction is executed, the breakpoint is replaced by the actual instruction, and a bit map is updated to indicate execution of the measured instruction. Execution resumes with the actual instruction.