Patent ID: 7165155

Claim:
In a data storage environment having a server, a first and second data storage system, and production data being stored on the first data storage system, and a copy of the data nominated as the data copy being stored on the second data storage system, a method of handling updates to the data copy, the method comprising the steps of: responsive to the start of an update to the copy of the data, marking the state of the production data as being ready for being incrementally copied to update the data copy to account for incremental changes to the production data since either a full copy or a prior incremental copy was performed, wherein the production data is marked in a data structure that includes a tracking data structure and a transfer data structure; preparing to update the data copy by protecting the production data from being written over until an incremental copy operation is performed by designating a current tracking data structure as the transfer data structure and a current transfer data structure as the tracking data structure; updating the data copy in accordance with the incremental copy operation being performed from the contents of the transfer data structure; and marking the state of the production data as having been transferred, and unprotecting the production data thereby allowing it to be written over by designating the transfer data structure as the current tracking data structure.