Lazy Recovery in a Hybrid Database Replication Protocol
Luis Ir, Antonio Calero-Monteagudo, Francesc D. Muò · 2003
COLUP is a hybrid database replication protocol that may be cong- ured to behave either as an eager or a lazy update protocol. When a faulty replica joins again the system, a recovery subprotocol is needed to update its database state. Independently of the chosen update strategy, these recovery tasks are lazy and introduce a minimal overhead in the non-recovering replicas. This recovery protocol is based on the roles carried out by each database replica when an object is considered. There are several roles: owner, synchronous, and asynchronous. The owner is unique and is the object creator. It manages the ac- cess control requests on its owned objects. Synchronous replicas are those that receive updates before transactions are committed. Finally, asynchronous repli- cas only receive lazy updates and may have a stale state. Thus, the recovering replica requests an up-to-date version of its owned objects once a local or re- mote transaction has made an access control request on them, but will rely on the common update propagation approach for all its non-owned objects.