Reliability refers to the percentage of time that an application is able to process correctly. In other words, an application may be available, yet unreliable if it cannot correctly handle the application processing. An example that we use to illustrate high availability but low reliability is a mobile phone network: While most mobile phone networks have very high uptimes (referring to availability), dropped calls tend to be relatively common (referring to reliability).
Oracle Coherence is explicitly architected to achieve very high levels of reliability. For example, server failure does not impact "in flight" operations, since each operation is atomically protected from server failure, and will internally re-route to a secondary node based on a dynamic pre-planned recovery strategy. In other words, every operation has a backup plan ready to go!
Oracle Coherence is architected based on the assumption that failures are always about to occur. As a result, the algorithms employed by Oracle Coherence are carefully designed to assume that each step within an operation could fail due to a network, server, operating system, JVM or other resource outage. An example of how Oracle Coherence plans for these failures is the synchronous manner in which it maintains redundant copies of data; in other words, Oracle Coherence does not gamble with the application's data, and that ensures that the application will continue to work correctly, even during periods of server failure.