A method, system, computer system, and computer program product to support
a distributed environment in which changes to data shared by multiple
nodes are logged using private logs and managed by a coordinator. The
coordinator recognizes invalidating operations and informs a reader when
data need to be read again after an invalidating operation corrupted
and/or caused the copy of the data read by the reader to be out-of-date.
The coordinator can provide a location from which current valid data can
be read. The coordinator can use an operations history to detect
invalidating operations and operations trackers to determine when a node
is not synchronized with the coordinator.