A parallel logging and recovery scheme for highly available main-memory
database systems is presented. A preferred embodiment called parallel
redo-only logging ("PROL") combines physical logging and selective replay
of redo-only log records. During physical logging, log records are
generated with an update sequence number representing the sequence of
database update. The log records are replayed selectively during recovery
based on the update sequence number. Since the order of replaying log
records doesn't matter in physical logging, PROL makes parallel
operations possible. Since the physical logging does not depend on the
state of the object to which the log records are applied, the present
invention also makes it easy to construct a log-based hot standby system.