Assign multiple storage control sessions with the SCSESSION keyword on the XADDPAIR command. Each storage control session has an independent SDM task that is committed to it. The system data mover is thereby capable of reading concurrently from each of the storage control sessions. Although it is possible to combine independent applications into a single session, this increases the SDM’s workload. Providing separate storage control sessions for each independent application achieves the best performance.
| You can configure up to . . . | For each . . . |
|---|---|
| 4 XRC sessions, and up to 64 combined XRC and CC sessions | Primary site 3990 or 9390 Storage Control |
| 64 combined XRC and CC sessions | Primary site ESS logical storage subsystem |
| 256 volumes | ESS logical storage subsystem |
| 128 volumes | 3990 or 9390 Storage Control |
| 80 storage control sessions | XRC session |
| 1 XRC session, and up to 16 combined XRC and CC sessions | volume |
| 20 XRC sessions (coupled or uncoupled) | Logical partition when in LPAR mode |
| 14 combined XRC coupled and cluster sessions | master CXRC session |
| 13 XRC sessions (coupled) | cluster session in the logical partition when in LPAR mode |
XRC maintains update sequence integrity among the volumes that you assign as part of an MVS XRC storage control session. The SDM, however, cannot maintain update sequence integrity between different XRC sessions unless the different sessions are coupled to the same master session. Therefore, if you are not running CXRC, keep all volumes associated with an application that requires update sequence integrity within the same MVS XRC session.