When you perform an IPL, the production IODF that defines the configuration to the system is selected and used. This IODF is selected from any number of other IODFs. You identify the IODF by the IODF statement in the LOADxx member of SYSn.IPLPARM or SYS1.PARMLIB PDS.
To identify the IODF selected at IPL, do the following:
- Identify the IODF volume. An IODF volume is the direct access
storage device (DASD) on which you place your IODFs. You identify
the IODF volume on the LOAD parameter on the operator control (OPRCTL)
or system control (SYSCTL) frame that is used when the system software
is loaded or in the LOAD profiles (for a 9672 Parallel Transaction
Server). See the processor documentation for more information. The IODF volume must be in the same subchannel set as
the IPL device.
On the LOAD parameter, you specify the device number of the IODF volume and the identifier for the LOADxx member. If you do not specify an IODF volume on the LOAD parameter, the system searches the sysres volume. If you do not specify a LOADxx member on the LOAD parameter, the system uses LOAD00.
The SYSn.IPLPARM or SYS1.PARMLIB PDS contains the LOADxx member. See Search order for the LOADxx member and IODF for a description of the order in which the PDSs are searched.
- In the LOADxx member, include an IODF statement that identifies the production IODF for IPL. For details about LOADxx, see z/OS MVS Initialization and Tuning Reference.
Figure 1 shows how the IODF is identified for IPL.
You can have multiple operating system and processor configurations in one IODF. The configurations can share common device definitions. In the IODF shown in the example, the configurations for operating system A and operating system C share EDT a.