Defining devices

Before you define a device that should be defined to an operating system and to the channel subsystem (CSS), you must have defined the operating system configuration, processor, channel path, and control unit. HCD omits some steps if data is missing. For example:

Defining device data

Defining multiple devices in one step

You can define, in one operation, a group of I/O devices of the same type and with consecutive device numbers. You define the group by specifying the first device number and the number of devices in the group. Then HCD applies the definition to all devices in the group. On the I/O Device List, you can type over the values that should be different.

Use and definition of serial number of device

HCD allows you to assign the same device number to more than one I/O device; that is, device numbers alone do not uniquely identify a device in an IODF. To clearly identify devices, HCD keeps track of each occurrence of the same device number by appending an internal suffix to the device number.

When activating a configuration dynamically, HCD might be unable to determine whether certain I/O devices in the currently active IODF and the IODF to be activated are physically the same. This may happen, if the new IODF was not created by copying or updating the current IODF but was newly created by migrating with IOCP or using the HCD dialog. In this case HCD is unable to determine which of the devices are physically identical.

To avoid problems when activating a configuration dynamically, you should check if more than one device uses the same device number attached to the same control units in the current IODF and in the newly created (not copied) IODF. If so, specify the same serial number for the devices that HCD should treat as physically the same.

Defining CSS-related definitions for a device

If you have defined a connection to a control unit on the Add Device panel, and the control unit is connected to a processor, then HCD displays the Device / Processor Definition panel (Figure 60) that shows the processors to which the control units are attached.

Figure 60. Device / Processor Definition

*--------------------- Device / Processor Definition -----------------------*
|                                                            Row 1 of 1     |
|                                                                           |
| Select processors to change device/processor definitions, then            |
| press Enter.                                                              |
|                                                                           |
| Device number  . . : 01E1           Number of devices  . : 8              |
| Device type  . . . : 3745                                                 |
|                                                                           |
|                                          Preferred  Device Candidate List |
|/ Proc.CSSID  SS+  UA+  Time-Out  STADET  CHPID +    Explicit         Null |
|_ XMPPRO1.0   __   05   No        Yes     __         No               ___  |
|_ G29.0       __   F0   No        No      __         No               ___  |
|_ G29.1       __   F0   No        No      __         No               ___  |
| ************************** BOTTOM OF DATA ******************************* |

Figure 61. Define Device / Processor

*-------------------Define Device / Processor -------------------------------*
|                                                                            |
|                                                                            |
| Specify or revise the following values.                                    |
|                                                                            |
| Device number  . . . : 01E1           Number of devices . . . . : 8        |
| Device type  . . . . : 3745                                                |
| Processor ID . . . . : XMPPRO1                                             |
| Channel subsystem ID : 0                                                   |
|                                                                            |
| Subchannel set ID  . . . . . . . _   +                                     |
| Unit address . . . . . . . . . . E1  + (Only necessary when different from |
|                                      the last 2 digits of device number)   |
| Time-Out . . . . . . . . . . . . No   (Yes or No)                          |
| STADET . . . . . . . . . . . . . Yes  (Yes or No)                          |
|                                                                            |
| Preferred CHPID  . . . . . . . . __  +                                     |
| Explicit device candidate list . No   (Yes or No)                          |

Defining the subchannel set for a device

Starting with z9 EC processors, each channel subsystem contains more than one subchannel set (SS 0, SS 1), where you can place the devices. Starting with z/OS V1R7 HCD, you can place PAV alias devices (types 3380A and 3390A) into an alternative subchannel set. In SS 0, you can place 63.75K devices, and in SS 1 you can place 64K-1 PAV alias devices.

Starting with zEnterprise processors, each channel subsystem contains a third subchannel set (SS 2). Starting with z/OS V1R10 HCD, you can place PAV alias devices (types 3380A and 3390A), PPRC secondary devices (type 3390D) and DB2 data backup volumes (type 3390S) into an alternate subchannel set. You cannot define 3390D and 3390S devices in subchannel set SS 0.

You can specify the subchannel set ID for a device either in column SS of Figure 60 or in field Subchannel set ID of Figure 61.

Note:

HCD messages that refer to a device in a subchannel set with a subchannel set ID > 0 will display the device number in the format n-devnumber where n is the subchannel set ID. For example, the device 1234 located in subchannel set 1 will show up as 1-1234. A device 4567 in subchannel set 0 will further on be shown as 4567.

Rules for placing devices into subchannel sets:

Observe the following rules and recommendations when working with different subchannel sets:

There is no required correspondence between device numbers in the subchannel sets. For example,
```
devices in the range 8000-807F in SS0
devices in the range 8000-807F in SS1 (PAV alias devices)
```
may relate to completely separate devices. However, you can use this feature to have PAV base and aliases in different subchannel sets, but with the same device numbers.
Unit addresses of base and alias devices on a single control unit must be unique. These cannot be duplicated across subchannel sets. So if you want to define the PAV base and alias devices in the range 8000-807F in different subchannel sets, but on the same control unit, you can define them like follows:
```
base  devices, range 8000-807F in SS0, unit address 00-7F  (CU number 8000)
alias devices, range 8000-807F in SS1, unit address 80-FF  (CU number 8000)
```
You can use dynamic reconfiguration to move eligible devices from SS 0 to an alternate subchannel set.

Restricting Partition Access for Devices

You can restrict logical partition access to an I/O device on a shared channel path by using the explicit device candidate list to select which logical partitions can access that I/O device. On the Define Device / Processor panel enter Yes or No in the Explicit device candidate list field to specify whether you want to restrict logical partition access to an I/O device:

If you specify Yes in the Explicit device candidate list field, the following panel is displayed, showing possible candidate partitions:

Figure 62. Define Device Candidate List

*------------------ Define Device Candidate List --------------------*
|                                                        Row 1 of 6  |
|                                                                    |
| Select one or more partitions to allow them to access the          |
| device, or ENTER to continue without selection.                    |
|                                                                    |
| Device number  . . . : 01E1      Number of devices  . . . : 8      |
| Device type  . . . . : 3745                                        |
| Processor ID . . . . : PROC1     This is the main processor        |
| Channel subsystem ID :                                             |
|                                                                    |
| / Partition Name  Description                       Reachable      |
| _ PROD1           First production partition        Yes            |
| _ PROD2           Second production partition       Yes            |
| _ TEST1           First test system                 No             |
| _ TEST2           Second test system                Yes            |
| _ TEST3           CF partition                      No             |
| _ TEST4           OS partition                      No             |

A Yes in the Reachable column indicates that the device can be reached from the respective partition, through at least one physical channel. You can only include reachable partitions into the explicit device candidate list by typing a slash ('/') into the action column. Deleting the slash means to remove the respective partition from the device candidate list.

Null device candidate list for XMP processors

If devices are connected to a control unit which is shared between multiple channel subsystems, some (not all) of these devices may specify an empty (or null) device candidate list for one or more CSSs. You create a null device candidate list for a device either by deselecting all candidate partitions from an existing list or by not selecting any partition for a new list.

If you define a null device candidate list of a device for a certain CSS, then no partition of this CSS may have access to the device. If you define an explicit device candidate list for a device, the Device / Processor Definition panel (Figure 60) indicates whether this candidate list is a null device candidate list in column Device Candidate List - Null. If no partition is allowed to have access to the device, value Yes is shown, otherwise value No. This field is left blank if no explicit device candidate list exists for the selected device (which is the default when creating new devices).