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.
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