Each device can be defined to one or more operating systems. The hardware configuration contains this definition information, known as the operating system (OS) configuration. Note that you may define devices and their associated parameters to an OS configuration, even if they are not explicitly connected.
Typically, the OS configuration is associated with a processor or partition. Each processor can run different OS configurations at different times. There are two types of OS configuration: MVS and VM.
An MVS OS configuration can contain one or more EDTs. An Eligible Device Table or EDT is a list of esoteric device groups, plus the names of the generic device types which determine how devices are used (order of preference) within each esoteric. The EDT is identified by a two-digit ID; you must define at least one EDT for each MVS OS configuration.
An esoteric device group or esoteric is an installation-defined and named grouping of I/O devices under an EDT. An esoteric acts as a single “virtual device” which can be allocated without using a specific device number. Devices within an esoteric are usually from the same device group, but can be of different device types.
Every device type is associated with a generic device group or generic. A generic is an MVS-defined grouping of devices with similar characteristics, which determines how devices are used in an esoteric device group. Each generic has a preference number which governs the order of allocation of devices to jobs within an esoteric. For example, if the esoteric contains the device types 3390, 3380 and 3350, and the generics associated with the device types have preference numbers 280, 290 and 300, respectively, then the preference numbers are used by the MVS allocation component to assign the devices in that order of preference.
Faster devices have lower preference numbers. You can change the preference number of a generic under an EDT (user-defined generic), but not under an OS configuration (system-defined generic).
You can mark one or more of the devices defined to an OS configuration to be your consoles. A console displays system-related information (for example, error messages) directly from MVS. For the MVS system, you can specify NIP consoles; for z/VM, you can specify primary and alternative VM consoles.
Under z/VM, you can only view z/OS IODFs, but you cannot define z/OS operation system configurations.