Automatic OSA Device Allocation

Whenever a shared port group is created, an instance of the port group is created on the z/VM® system the command was issued and also created (propagated) in each active IVL member (instance 0). By specifying a device number for a shared port group you are actually selecting an Start of changeOSAEnd of change adapter; not a specific device. To select an Start of changeOSAEnd of change adapter, specify a single device number configured for the target Start of changeOSAEnd of change adapter (PCHID) and the port number (for an Start of changeOSA-ExpressEnd of change multiport adapter). The device number that is selected by z/VM might be different from the device number that you specified on the SET PORT GROUP JOIN command.

The scope of Start of changeOSAEnd of change device allocation for a shared port group is as follows:

  • When an Start of changeOSAEnd of change adapter is added to a SHARED Port Group, all devices on the same PCHID will be RESERVED for system use (SYSTEM device) and will be propagated to every z/VM system in the IVL domain.
  • z/VM will allocate a device from the SYSTEM list when adding (JOIN) a device to a SHARED Port Group or an additional instance of a group.
  • All device numbers (subchannels) used within a SHARED Port Group are allocated by z/VM and not necessarily the ones specified on a SET PORT GROUP JOIN command.
  • A SYSTEM device cannot be attached or dedicated to a virtual machine.
  • All devices on the same Start of changeOSAEnd of change adapter (PCHID) must be removed from all instances of a SHARED Port Group before they can be attached to a virtual machine.