Defining devices to a subset of logical partitions

You can limit I/O device access from LPs to I/O devices assigned to shared channels by using IOCP or HCD to specify device candidate lists. By defining devices attached to a control unit to a subset of LPs, you can manage which LPs attempt to establish logical paths to the control unit through a shared channel.

If you define no devices to a control unit from a particular LP, the shared channel associated with the LP does not attempt to establish a logical path. However, if there is at least one device defined to the control unit for the shared channel associated with a particular LP, the shared channel for the LP attempts to establish a logical path to the control unit for the LP.

In Figure 1, LP access to a series of control units is managed through use of the device candidate lists for the I/O devices attached to the control units. The shared FICON channel attempts to establish only one logical path to each of the control units even though 5 LPs share the channel.

In the example, the channel only attempts to establish a logical path for LP1 to the control unit defined as number 10 because only LP1 has a device defined to that control unit. Similarly, only LP2 can access control unit 11, only LP3 can access control unit 12, only LP4 can access control unit 13, and only LP5 can access control unit 14.