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Subchannel numbers are usually not required by the operator and are not displayed in the output from any operator commands. The contents of the subchannel can be displayed on the HMC. Two types of information can exist in a subchannel: ­ Static information, such as which CHPIDs can access the device, is obtained from the IOCDS. ­ Dynamic information reflects the current state of the device and the current I/O operation. When subchannels are built (at POR time) they are left in a disabled state. They are also disabled during the initial stage of IPL. Subsequently, in IPL processing, z/OS attempts to match devices (UCBs) and subchannels (UCWs). Any subchannel that has a matching UCB is enabled for that LPAR. All the I/O data contained in IOCDS is used by the channel subsystem; control units are not aware of the IOCDS. Certain devices are not defined in HCD or HCM, but are represented by a subchannel number, such as the ADMF function and cryptographic PCI-CC. 4.9 Paths A path is simply a route to a device. From an operation system point of view, a path flows from the UCB, which represents the device to z/OS, through the subchannel (UCW, which represents the device in the channel subsystem), over a channel, possibly through a director (switch), and through the control unit