Although conventional database management systems are designed to tolerate hardware and to a lesser extent even software errors, they cannot protect themselves against syntactically correct and semantically damaging transactions, which could arise because of malicious attacks or honest mistakes. The lack of fast post-intrusion or posterror damage repair in modern DBMSs results in a longer Mean Time to Repair (MTTR) and sometimes permanent data loss that could have been saved by more intelligent

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... repair mechanisms. In this paper, we describe the design and implementation of Phoenix -a system that significantly improves the efficiency and precision of a database damage repair process after an intrusion or operator error and thus, increases the overall database system availability. The two key ideas underlying Phoenix are (1) maintaining persistent intertransaction dependency information at run time to allow selective undo of database transactions that are considered "infected" by the intrusion or error in question and (2) exploiting information present in standard database logs for fast selective undo. Performance measurements on a fully operational Phoenix prototype, which is based on the PostgreSQL DBMS, demonstrate that Phoenix incurs a response time and a throughput penalty of less than 5% and 8%, respectively, under the TPC-C benchmark, but it can speed up the postintrusion database repair process by at least an order of magnitude when compared with a manual repair process.