Lec 17 MIT 6.033 Computer System Engineering, Spring 2005
Good afternoon. So we're going to continue our discussion about atomicity and how to achieve atomicity. And today the focus is going to be on implementing this idea called recoverability, which we just described and defined the last time. So if you recall from last time, the idea is that when you have modules that interact with one another, and in this example M1 calls M2, and M2 fails somewhere in the middle of this invocation and it recovers, the goal here is to try to make sure that the invoker of this module, in this case M1, or all subsequent invokers of M1, don't see any partial results that were computed during this execution when M2 failed. And this was the idea that we called recoverability. And the definition of recoverability was that an action, which is made up of a composite sequence of steps is recoverable from the point of view of its invoker, if it looks to the invoker and to all subsequent invokers as if this action either completely occurred, or ...