Deciding on the number of IODFs

The decision whether to create one IODF for each processor, or to combine the I/O definitions for two or more processors in a single IODF, depends on your environment. This section explains when it is advantageous or even necessary to keep the I/O definitions of two or more processors in the same IODF.

Shared control units and devices

If control units and devices are shared by different processors, the I/O definitions for these processors should be kept in the same IODF to keep change effort to a minimum and to avoid conflicting definitions.

Processor and related OS configuration(s)

For a full dynamic reconfiguration, the IPLed OS configuration must be in the same production IODF as the processor configuration selected for POR.

Coupling facility support

For coupling facility support, you have to maintain your coupling facility definitions for the processors to be connected in the same IODF.

Switch connections

It is recommended that you maintain your switch configurations in the same IODF as the hardware and software configuration definitions to provide complete validation of the data path.

In order to lookup the port connections of a switch, all connected objects to the ports of a switch have to be defined in the same IODF.

CPCs of a System z cluster

To manage IODFs, IOCDSs, and IPL parameters within the CPCs of a System z cluster from a focal-point HCD, the corresponding processor configurations have to be kept in the same IODF.

Dynamic sysplex reconfiguration

To dynamically reconfigure the I/O configuration of a system within a sysplex from a focal-point HCD, the processor and OS configuration of the sysplex system have to be defined in the same IODF.

CTC connection report

All CTC connections listed in a CTC connection report must be defined in the same IODF. Misconfigurations can be detected only within the scope of one IODF.

Reporting

The scope of the reports (textual or graphical) is a single IODF. All I/O definitions required for a report must be kept in the same IODF.

Validation

The scope of the validation function is a single IODF.

HCM

The scope of the configuration shown by HCM is a single IODF.

These requirements and recommendations may lead to a large IODF, depending on the size of the installation. The number of elements in the single IODF may be too large for effective management. HCD provides the possibility of creating manageable subset IODFs with a scope limited to a part of the I/O configuration from a master IODF describing the entire configuration. For details on this IODF management strategy refer to The master IODF concept.