Migrating Simplex Volume

The following procedure is used to migrate simplex volumes, that is, volumes that are not already part of a duplex pair. This procedure is valid for any two devices qualified to be part of a duplex pair.

  1. Vary the target secondary volume offline to all attached systems.
  2. Issue SETCACHE SETSECONDARY.
  3. After the copy completes, issue SETCACHE SUSPENDPRIMARY.
  4. Issue SETCACHE RESETTOSIMPLEX.
  5. The original device is no longer in use. The application continues to access the same UCB (MVS™ device address), but is using a different physical device.
  6. Proceed with required activities. Use ICKDSF to change the volser if required.
Note: When you use dual copy to migrate from 3390 devices to RAMAC devices, an invalid format 4 DSCB is created on the target device. Use ICKDSF to fix the format 4 DSCB. See your IBM® representative for the latest service level of ICKDSF that provides this function.

If DASD fast write was active before this procedure was executed, it remains active after the procedure completes.

  1. Before the duplex pair is established, the channel connection address (CCA), which is known to MVS, and the director to device connection (DDC) address, which is the physical address known within the subsystem, are the same as when initialized.
  2. After creating the duplex pair, both addresses directly correlate.
  3. When SETCACHE SUSPENDPRIMARY is issued, the Storage Control swaps the CCA-to-DDC assignments between the primary and the secondary volumes.
  4. The system application continues to use the UCB for device 201. However, the Storage Control directs the I/O to the physical device addressed by DDC 12 (the target volume). The UCB for the offline device 212 still points to CCA 12, but the Storage Control points CCA 12 to the suspended device (DDC 01).
  5. When SETCACHE RESETTOSIMPLEX is issued, the Storage Control maintains the swapped CCA-to-DDC pointers.
Parent topic: Using SETCACHE