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Replication Schemes For Mobile Environment
•Eager Replication: It attains replication by keeping all replicas
exactly synchronized at all nodes. This in turn is achieved by
updating all replicas in one transaction. No concurrency
anomalies occur since eager replication gives serializable
execution. Eager replication is not a proper choice for a
mobile environment since eager replication reduced update
performance with extra updates, and in a mobile environment
the nodes are normally disconnected.
•Lazy Replication: These algorithms are more suited to the
mobile environment . The synchronization occurs after the
updating transactions commits. That is, replication is
asynchronous in nature. The problem with lazy replication is
that it may allow a transaction to see a very old committed
value.
