IBM Z9, Planning Manual

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When an I/O configuration is dynamically modified so the logical partition can gain
access to a device not previously accessible, a device conflict can occur. The
conflicts are detected when commands are processed that change the I/O
configuration or when you attempt to activate the logical partition which has the
device number conflict. A message displays identifying the error.
The identified device cannot be accessed while a conflict exists. Two types of
conflict are possible:
v Conflicts between device numbers for the same device (a shared device)
v Conflicts between device numbers for different devices (unshared devices)
Activation fails if a duplicate device number conflict exists.
Examples of Duplicate Device Number Conflicts: Figure 2-17 provides two
examples of duplicate device number conflict.
The following example shows the IOCP statement for Figure 2-17. 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
creates a duplicate device number conflict for device number 180 when the devices
are connected to two different control units. This occurs because a device
numbered 180 already exists on the original channel path 10. If such conflicts
occur, the operator must know what configuration is desired.
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 may result in a
performance problem because the control program in logical
partition OS390 cannot access the device from channel path 4.
ZOSPROD ZOSPROD
Device 180
Example, Shared Device Example, Unshared Device
CHP
00
CHP
04
CHP
00
CHP
04
CHP
04
CHP
10
CHP
04
CHP
10
Device 180 Device 180
ZOSTEST ZOSTEST
Figure 2-17. Two Examples of Duplicate Device Number Conflicts
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PR/SM Planning Guide