A fundamental problem in programming is error recovery. After an error, your application must restore itself to the state it had before the error took place. Consider an application that tries to perform an operation comprising several smaller operations, potentially concurrently, where each of the individual operations can fail or succeed independently of the others. An error in any one of the smaller operations means the system is at an inconsistent state. Take a banking application, for example, that transfers funds between two accounts by crediting one account and debiting the other. Successfully debiting one account but failing to credit the other is an inconsistent state, because the funds cannot be in both places at the same time, and failing to debit while successfully crediting results with an equally inconsistent state in which the money is gone. It is always up to the application to recover from the error by restoring the system to the original state.
展开▼
