Using channels

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Figure 1 shows an example of an I/O configuration with a device shared by each of the four logical partitions. In this representation of a shared device, each logical partition views device 190 as part of its own I/O configuration. Notice the recoverability characteristics of this configuration: each logical partition has two channel paths to the shared device, each attached to a different storage director.

Figure 1. Physical connectivity of shared device 190

The following example shows the IOCP statement for Figure 1.

CHPID PATH=(10),PART=(A,REC)
CHPID PATH=(14),PART=(A,REC)
CHPID PATH=(18),PART=(B,REC)
CHPID PATH=(1C),PART=(B,REC)
CHPID PATH=(20),PART=(C,REC)
CHPID PATH=(24),PART=(C,REC)
CHPID PATH=(28),PART=(D,REC)
CHPID PATH=(2C),PART=(D,REC)
CNTLUNIT CUNUMBR=0001,PATH=(10,18,20,28),UNITADD=((90)) . . .
CNTLUNIT CUNUMBR=0002,PATH=(14,1C,24,2C),UNITADD=((90)) . . .
IODEVICE ADDRESS=(190),CUNUMBR=(0001,0002) . . .

If 8 or less channels attach to the device, this method of defining the IOCP input provides greater flexibility because it allows you to move CHPIDs from one LP to another and eliminates possible conflicts (see Figure 2).

Figure 2 shows an alternative method of defining the configuration. This method is required if there are greater than eight paths to the device. This logical representation has the same recoverability characteristics as the physical connectivity:

Each LP has two channel paths to the shared device
Each LP is attached to a different storage director

However, paths cannot be moved between the LPs.

Figure 2. Logical view of shared device 190

The following example shows the IOCP statement for Figure 2.

CHPID PATH=(10),PARTITION=(A), . . .
CHPID PATH=(14),PARTITION=(A), . . .
CNTLUNIT CUNUMBR=0001,PATH=(10),UNITADD=((90)) . . .
CNTLUNIT CUNUMBR=0002,PATH=(14),UNITADD=((90)) . . .
IODEVICE ADDRESS=(190),CUNUMBR=(0001,0002) . . .

CHPID PATH=(18),PARTITION=(B), . . .
CHPID PATH=(1C),PARTITION=(B), . . .
CNTLUNIT CUNUMBR=1001,PATH=(18),UNITADD=((90)) . . .
CNTLUNIT CUNUMBR=1002,PATH=(1C),UNITADD=((90)) . . .
IODEVICE ADDRESS=(190),CUNUMBR=(1001,1002) . . .

CHPID PATH=(20),PARTITION=(C) . . .
CHPID PATH=(24),PARTITION=(C) . . .
CNTLUNIT CUNUMBR=2001,PATH=(20),UNITADD=((90)) . . .
CNTLUNIT CUNUMBR=2002,PATH=(24),UNITADD=((90)) . . .
IODEVICE ADDRESS=(190),CUNUMBR=(2001,2002) . . .

CHPID PATH=(28),PARTITION=(D), . . .
CHPID PATH=(2C),PARTITION=(D), . . .
CNTLUNIT CUNUMBR=3001,PATH=(28),UNITADD=((90)) . . .
CNTLUNIT CUNUMBR=3002,PATH=(2C),UNITADD=((90)) . . .
IODEVICE ADDRESS=(190),CUNUMBR=(3001,3002) . . .