1. In a data processing system storing a first and a second version of a given data set, a method for synchronizing the first and second versions, comprising: maintaining a sync-complete control field and a sync-in-progress control field corresponding to each of the first and second versions, the sync-complete control field indicating when set that the corresponding version is synchronized and the sync-in-progress control field indicating when set that the corresponding version is in the process of being synchronized; clearing the sync-complete control field and the sync-in-progress control field in response to a change in the corresponding version; first detecting the sync-complete control field for the first and second versions, and if either or both are cleared, then setting the sync-in-progress control field corresponding to a selected version of the first and second versions; transferring a copy of the selected version to a temporary file to establish a temporary version; second detecting the sync-in-progress control field in the selected version, and if it is set when the temporary version is complete, then setting the sync-complete control field and clearing the sync-in-progress control field corresponding to the selected version; setting the sync-complete control field in the temporary version; renaming the temporary version to the one of the first and second versions not selected in the first detecting step and removing the one not selected in the first detecting step.