Dynamically changing component definitions

You can dynamically add, modify, or delete components in the configuration. You can make software and hardware changes or software-only changes. In most cases, you will make simultaneous dynamic configuration changes to both hardware and software configuration definitions. The following sections describe how to dynamically change component definitions. For software-only changes, you do not have to perform all the steps. It is noted when the step is not required for a software-only change.

Any dynamic configuration addition, modification, or deletion requires the following two general steps:

Describe the new I/O configuration definition in an I/O definition file (IODF) that you create through HCD. See z/OS HCD User's Guide.
Activate the new IODF.
You can use either HCD panels or the ACTIVATE command to dynamically activate or test a new I/O configuration definition. Generally, system programmers use HCD and system operators use the ACTIVATE command. To use HCD panels, see z/OS HCD User's Guide. To use the ACTIVATE command, see z/OS MVS System Commands.
Note:
1. For software/hardware changes, activate “hardware and software definitions”. Also, write a new I/O configuration data set (IOCDS) for the new default IOCDS at the next POR.
2. For software-only changes, activate “software definitions only.” You can also choose to “validate hardware changes,” which validates that I/O components being deleted are not in use.

Additional steps related to specific I/O components are described in

Coupling facility device and control unit definitions in the IODF are created or deleted automatically when coupling facility channel paths are connected or disconnected. See Making changes to coupling facility devices and control units.