Creating a Duplex Pair from Two Simplex Volumes

The procedure to create a duplex pair is:

  1. Identify the primary and secondary volumes
  2. Issue SETCACHE SUBSYSTEM ON
  3. Vary the target secondary volume offline to all systems
  4. SETCACHE NVS ON
  5. SETCACHE SETSECONDARY specifying the primary volume id and secondary address
  6. SETCACHE DEVICE ON for the primary volume
  7. (optional) SETCACHE DASDFASTWRITE ON
Note:
  1. If DASD fast write or device caching was on for the primary volume before SETCACHE SETSECONDARY was issued, DASD fast write or device caching is on for the pair after it is established.
  2. Device caching may be activated to speed up establishing the duplex pair.
  3. When you use dual copy to migrate from 3390 devices to RAMAC devices, an invalid format 4 DSCB is created on the target device. An ICKDSF APAR must be installed to fix the format 4 DSCB. See your IBM® representative for the latest service level.
  4. If either volume was previously acquired by an LPAR and has not been released, an error message is issued with text that states that the duplex pair could not be established because path-groups are not compatible.
Parent topic: Using SETCACHE