Examples of duplicate device number conflicts

Figure 1 provides two examples of duplicate device number conflict.

The following example shows the IOCP statement for Figure 1. Both examples use identical IOCP statements.

CHPID PATH=(00),PARTITION=(ZOSPROD,REC)
CHPID PATH=(04),PARTITION=(ZOSPROD,REC)
CNTLUNIT CUNUMBR=0001,PATH=(00,04),UNITADD=80
IODEVICE ADDRESS=180,CUNUMBR=0001

CHPID PATH=(10),PARTITION=(ZOSTEST)
CNTLUNIT CUNUMBR=0002,PATH=(10),UNITADD=80
IODEVICE ADDRESS=180,CUNUMBR=0002

Channel path 04 is reassigned from ZOSPROD to ZOSTEST in each example. This reassignment creates a duplicate device number conflict for device number 180 when the devices are connected to two different control units. This conflict occurs because a device numbered 180 exists on the original channel path 10. If such conflicts occur, the operator must know what configuration is wanted.

Shared device

In the example on the left, the duplicate device numbers refer to the same device from different logical partitions (a new path to the same device has been moved to ZOSTEST). This situation might result in a performance problem because the control program in logical partition ZOSPROD cannot access the device from channel path 4.

Unshared Device

In the example on the right, the duplicate device numbers refer to a different device from each logical partition (a new device has been moved to ZOSTEST). This situation might result in a data integrity problem because the control program in logical partition ZOSTEST cannot access the correct device from channel path 04.