Input/output definition file (IODF)

An input/output definition file (IODF) contains information about the I/O configuration, such as:

Operating system data
Switch data
Device data, including EDT definition
Processor data
Partition data
Channel path data
Control unit data
Channel subsystem data.

Three types of IODF exist: a work IODF, a validated work IODF, and a production IODF.

Work IODF: A work IODF allows you to create a new I/O configuration definition or modify an existing I/O configuration definition. A work IODF provides a way to build or modify an IODF before you use it to activate a configuration. It is a working copy, not suitable for IPL selection or activated during dynamic activation. When a work IODF is ready to use, build a production IODF from it.
Validated work IODF: A validated work IODF satisfies all validation rules for building production IODFs. It may lack at least one physical channel identifier (PCHID). In cooperation with HCD and the CHPID Mapping Tool a validated IODF is required to accept new or updated PCHIDs. From such a validated work IODF, an IOCP input deck suitable for use with the CHPID Mapping Tool is generated. As soon as all PCHIDs are inserted or updated in the validated work IODF, the production IODF can be built. In HCD, you can use various methods to obtain a validated work IODF.
Production IODF: A production IODF defines one or more valid I/O configurations. A configuration in a production IODF can be activated dynamically or selected during IPL. Although you can build multiple production IODFs, only the one that is selected during IPL or activated during dynamic configuration is the active production IODF.

To change a configuration, create a work IODF from a production IODF. When you attempt to change a production IODF, HCD automatically copies the production IODF into a work IODF so you can make your changes. When changes are complete, build a production IODF from the work IODF.

You can organize your configuration data in an IODF in multiple ways. For example:

You can define multiple operating system and processor configurations in one IODF. The configurations can share common device definitions; this reduces the maintenance effort when devices are changed.
For a processor that supports logical partitions, you can define the configurations for the processor and the operating systems running in the logical partitions of that processor in one IODF.
From the IODF representing the complete configuration (master IODF), you can create IODFs containing parts of the whole configuration (for example, a processor with all of its relevant operating systems). These IODFs can be distributed to a target system and used for activation. Note that the processor token does not change during the distribution process. You can also merge distributed IODFs in the master IODF. For information about handling large IODFs, see z/OS HCD User's Guide.
You can define several IODFs for the same hardware, with different configurations for use in different circumstances. However, this approach is not recommended, because you might need to update multiple IODFs when you change the configuration.