Dynamically adding I/O devices

To dynamically add an I/O device, use the following general steps:

1. For each device that you plan to add, ensure that its device support code was loaded at the last IPL.
   There are two ways which device support code is loaded at IPL. The choice made at the last IPL can determine whether the device support code is loaded for the device that you want to add. Through the IODF statement in the LOADxx member of SYS1.PARMLIB, or SYSn.IPLPARM, for the last IPL, you might have chosen either of the following:

   • To load, at IPL, all the dynamic device support code in SYS1.NUCLEUS.

     This choice, which is the default, allows you to dynamically add any device that supports dynamic configuration.

   • To load, at IPL, device support code for only those device types defined in the IODF. This choice allows you to dynamically add only those device types that were defined in the IODF.

     If you add a new device and the device support code for that new device was not loaded at IPL, your system cannot use that device. Before your installation can use that device, you must reIPL the system to load the device support code.

   After a HyperSwap® failover swap has occurred, ensure that if a Special Secondary (3390D) device is being added, a 3390B PPRC primary device with the same four-digit device number is also being added. If one device in a Special PPRC pair (3390B/3390D) is not being added when the other device in the pair is being added, the dynamic activate will fail.

   In general, devices, including PPRC secondary (3390D) devices in an alternate subchannel set, can be dynamically added at any time. However, since 3390D devices are accessible through their corresponding partner devices in the primary subchannel set, adding such devices without their primary partners either already existing or being added at the same time will leave those 3390D devices inaccessible and, therefore, unusable.

   After a HyperSwap failover swap has occurred, adding PPRC secondary (3390D) devices to the active subchannel set while their corresponding partners in the primary subchannel set already exist will not be allowed since the newly added devices, which may not contain the most up-to-date data, will replace their primary partner devices as the active devices.

   For details about specifying your choice at IPL, see IODF processing at IPL.

2. Describe the new I/O configuration definition in an I/O definition file (IODF) that you create through HCD. Including an I/O component in an IODF adds that I/O component's definition to the I/O configuration definition.
3. Activate the new IODF using the steps in Dynamically changing an I/O configuration in hardware.
4. Install the new I/O devices that you have dynamically added through the new IODF. Vary the added devices online to eligible systems using the corresponding system commands. New and not yet formatted disk devices should be formatted in offline mode prior to varying them online.

Besides these general actions to add a device, other actions might be required to make certain devices usable. For example, adding a direct access storage device (DASD) to support a page data set requires the following actions:

1. For the DASD that you plan to add, ensure that device support code was loaded at the last IPL.
2. Create a new I/O definition file (IODF) that defines the DASD to both hardware and software.
3. Activate the new IODF.
4. Install the DASD.
5. Run the ICKDSF program to format a volume on the DASD.
6. Vary the DASD online to z/OS®.
7. Run IDCAMS to define the page data set on the DASD.
8. Enter the PAGEADD command to add the page data set.

z/OS directs paging activity to the volume.