As mentioned in Determining Whether zHPF is Supported for a Device, you must make sure that a device supports zHPF as well as all the zHPF functions your channel program requires before issuing an EXCP or EXCPVR request for a zHPF channel program. In addition, even if the processor and device support zHPF and all the zHPF functions required, these might be disabled when you actually submit your channel programs:

• zHPF itself might be disabled on a processor and device that supports it when you submit your channel program for any of the following reasons:
  • The operator issued a command to disable zHPF for the system
  • The zHPF feature is no longer enabled for the control unit associated with the device
  • Internal errors have occurred that caused zHPF to be disabled for the device
  • The device used in the EXCP or EXCPVR request has been swapped to a device that does not support zHPF.
  When the device no longer supports zHPF, the IOB completion code (IOBECBCC) is set to X'41' and the reason code (IOBERCOD) is set to X'0E'. You can retry the EXCP or EXCPVR request by creating a CCW channel program and either reissuing the EXCP or EXCPVR request, or returning at offset +8 in your abnormal end appendage to execute a new channel program.
• Some required zHPF functions might be disabled on a supporting processor and device if you swap to a device that does not support all required zHPF functions. In that case, you must evaluate the zHPF functions that are supported on that device to determine whether you still can use a zHPF channel program or whether you must substitute a CCW channel program instead.