Defining CTC control units

When you define FICON® CTC control units, an unshared channel at the other end of a CTC connection is associated with a single CTC control unit. When you have a shared channel at the other end of a CTC connection, each partition sharing the channel path is associated with a separate control unit. It does not matter which channel actually has the FICON CTC control unit function.

• If the CTC connection is through a FICON Director, specify the port address of the channel at the other end of the CTC connection with the LINK keyword in the CNTLUNIT statement for that channel.
• If the CTC connection is point-to-point, do not specify the LINK keyword in the CNTLUNIT statement.

Control unit type keyword UNIT must be coded as FCTC to enable the CTC control unit in the FICON channel. Also, the unit addresses specified for each CTC connection must be identical. For the FICON CTC connection to be successful, at least one end of the connection must be on the following CPC:

• IBM® Z and LinuxONE general purpose models at EC J10638 or later.

The other end of the FICON CTC connection can be on any CPC that supports FC channel paths. If neither FC channel path is on a CPC listed above, no FICON CTC connection will be established and the CTC devices will be unusable.

When connecting to a shared channel path (as System B is doing with CHPID 50 in System A), it is necessary to specify a control unit for each logical partition that the shared CHPID has access to and with which you want to communicate. Also, it is necessary to identify to which logical partition each control unit is associated. This is accomplished by specifying the partition number or CSS ID and MIF image ID of the destination partition in the CUADD keyword. When communicating to a shared FC channel path on a System z9® or zSeries processor other than a z/800 or z/900, the CUADD keyword value must be two digits if the destination logical partition has a non-zero CSS ID. For example, if the destination logical partition is in CSS 1 and has MIF image ID 5, specify CUADD=15.

Do not code the CUADD keyword if the destination CHPID is not shared.

Define a CTC control unit for each destination partition to which you want to connect. For System A, specify the following:

CNTLUNIT CUNUMBR=4B10,PATH=50,LINK=D0,UNITADD=((40,8)),UNIT=FCTC

For System B, specify the following:

CNTLUNIT CUNUMBR=5A10,PATH=60,LINK=C0,UNITADD=((40,8)),UNIT=FCTC,CUADD=1 
CNTLUNIT CUNUMBR=5A20,PATH=60,LINK=C0,UNITADD=((40,8)),UNIT=FCTC,CUADD=2
CNTLUNIT CUNUMBR=5A30,PATH=60,LINK=C0,UNITADD=((40,8)),UNIT=FCTC,CUADD=3 

All three partitions in System A will use control unit 4B10 to communicate with partition LP1B in System B. System B will use control unit 5A10 to communicate with partition LP1A in System A, control unit 5A20 to communicate with partition LP2A and control unit 5A30 to communicate with partition LP3A.

Using the recommended control unit numbering method described in Chapter 3, we could assign CTC image IDs of A1 to LP1A, A2 to LP2A, A3 to LP3A and B1 to LP1B. We would also define separate Send and Receive control units. But to do so requires a second pair of FC channels. Assume CHPID 51 is on System A, connects to port C1 on the FICON Director, and is shared by the same partitions as CHPID 50. Assume CHPID 61 is on System B, connects to port D1 on the FICON Director, and is dedicated to partition LP1B. For System A, we could specify the following:

CNTLUNIT CUNUMBR=4B10,PATH=50,LINK=D0,UNITADD=((40,8)),UNIT=FCTC 
CNTLUNIT CUNUMBR=5B10,PATH=51,LINK=D1,UNITADD=((40,8)),UNIT=FCTC

For System B, we could specify the following:

CNTLUNIT CUNUMBR=4A10,PATH=61,LINK=C1,UNITADD=((40,8)),UNIT=FCTC,CUADD=1
CNTLUNIT CUNUMBR=4A20,PATH=61,LINK=C1,UNITADD=((40,8)),UNIT=FCTC,CUADD=2
CNTLUNIT CUNUMBR=4A30,PATH=61,LINK=C1,UNITADD=((40,8)),UNIT=FCTC,CUADD=3
CNTLUNIT CUNUMBR=5A10,PATH=60,LINK=C0,UNITADD=((40,8)),UNIT=FCTC,CUADD=1
CNTLUNIT CUNUMBR=5A20,PATH=60,LINK=C0,UNITADD=((40,8)),UNIT=FCTC,CUADD=2
CNTLUNIT CUNUMBR=5A30,PATH=60,LINK=C0,UNITADD=((40,8)),UNIT=FCTC,CUADD=3

This would result in control unit 4B10 sending data to be received by control units 5A10-5A30 and control units 4A10-4A30 sending data to be received by control unit 5B10.