Defining one or more separate, low-activity volumes specifically for system data mover I/O activity is helpful for storage subsystems that do not have the functional capabilities of the ESS storage subsystem. By having a dedicated reader volume, the system data mover can avoid conflicts with application programs that share a utility volume. Sharing a utility volume can negatively impact the performance of both the SDM and the application program.
The XRC system data mover software issues its I/O to the XRC utility volume that is associated with each primary storage control. This is part of the data transfer process. You may assign one or more XRC utility volumes to each primary storage control by specifying the SCSESSION keyword on the XADDPAIR command. Each specified unique SCSESSION will start a separate reader. All volumes in an LSS (or SSID) with the same SCSESSION share the same reader.
For additional information about using XRC utility devices, refer to Using XRC utility devices.