Synchronization of accesses to shared data and recovering the state of such data in the case of failures are really two aspects of the same problem--implementing atomic actions on a related set of data items. In this paper a mechanism that solves both problems simultaneously in a way that is compatible with requirements of decentralized systems is described. In particular, the correct construction and execution of a new atomic action can be accomplished without knowledge of all other atomic

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... ons in the system that might execute concurrently. Further, the mechanisms degrade gracefully if parts of the system fail: only those atomic actions that require resources in failed parts of the system are prevented from executing, and there is no single coordinator that can fail and bring down the whole system.