When the initialization is complete, DFSMSdss releases serialization and calls the UIM, as described in the previous topic. DFSMSdss then starts to read the data to perform the dump or copy operation. Applications can resume processing the data while concurrent copy is making the copy. Meanwhile, the cached storage subsystems monitor the I/Os for updates to any tracks that are included in the concurrent copy session.
DFSMSdss uses the SDM to read data from the devices within the concurrent copy session. For data that was not included in the concurrent copy session, DFSMSdss reads the data itself in the same way as for a nonconcurrent copy operation. As DFSMSdss receives tracks from the SDM or reads them itself, it writes the data to the output device in the same way as for any DFSMSdss operation.