A computer program product, according to one embodiment, includes a computer readable storage medium (which is not a transitory signal per se) having program instructions embodied therewith which are readable and/or executable by a processor to cause the processor to perform a method which includes: receiving data at a secondary storage volume in a secondary system from a primary storage volume in a primary system. Upon receiving a read request at the secondary system, the method includes: reading the requested data from the secondary storage volume; sending a request to the primary system for the requested data after determining that it is not in the secondary storage volume; receiving the data from the primary system; supplying the requested data; storing the data received from the primary system in the secondary storage volume; updating a secondary record; and sending a message to the primary system for updating a primary record.