SHADOW_SYS_UNIT

   Use this parameter for Phase II shadowing only. The SHADOW_SYS_
   UNIT parameter is an integer value that contains the virtual unit
   number of the system disk. The default value is 0. The maximum
   value allowed is 9999. This parameter is effective only when the
   SHADOW_SYS_DISK parameter has a value of 1. This parameter should
   be set to the same value on all nodes booting off a particular
   system disk shadow set. See VSI Volume Shadowing for OpenVMS
   for more information about setting system parameters for volume
   shadowing.