Improving data freshness in lazy master schemes

Abstract

Many distributed database applications need to replicate data to improve data availability and query response time. The two phase commit protocol guarantees mutual consistency of replicated data but does not provide good performance. Lazy replication has been used as an alternative solution in several types of applications such as online financial transactions and telecommunication systems. In this case, mutual consistency is relaxed and the concept of freshness is used to measure the deviation between replica copies. We propose two update propagation strategies that improve freshness. Both of them use immediate propagation: updates to a primary copy are propagated towards a slave node as soon as they are detected at the master node without waiting for the commitment of the update transaction. We study the behavior of our strategies and show that they improve data freshness with respect to the deferred approach.