Migrating Duplex Volumes
This procedure is valid for migrating a primary or secondary volume
in a duplex pair to another like device.
- Vary the target volume offline to all systems.
- Issue SETCACHE SUSPENDSECONDARY or SUSPENDPRIMARY, depending on whether the secondary or the primary, respectively, needs to be taken out of the duplex pair.
- Issue SETCACHE REESTABLISHDUPLEX with the third volume.
- After the copy completes, perform the required action for the volume suspended from the duplex pair.
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.
- When the SETCACHE SUSPENDPRIMARY completes, the system device number points to the CCA address of the old primary volume. Internally, the Storage Control has swapped the CCA-to-DDC pointers. The old primary CCA now points to the old secondary physical device DDC. Thus, the old secondary volume has become the new primary volume; all system I/O is directed to the new primary. The CCA for the old secondary volume now points to the DDC address of the old primary device.
- After the REESTABLISHDUPLEX completes, the new secondary is incorporated into the duplex pair, the old primary volume is no longer in the pair, and the CCA of the old secondary now points to the DDC address of the old primary. To run ICKDSF or any other program against the old primary volume, the old primary should be addressed as 212.