IBM RT PC Problem Determination Manual page 261

Invalid IOCN in the file name (non-fatal)
20
Cause: The field containing the four character IOCN
value is invalid for some file name in the loadlist. This
field must contain a hexadecimal value from X' 0001' to
X' 04001 for any module that has an IOCN. This field
must be X' 0000' for any module that does not have an
IOCN.
The
VRM Programming Support
information on the naming conventions for modules in
the loadlist. The loadlist processor will skip this module
and continue processing after displaying the error.
Action: If the VRM minidisk has been changed by
adding additional, remove or rename the module with
the invalid file name.
21 Invalid IOCN in the DDS (non-fatal).
Cause: A module that has been executed by the loadlist
processor (permission bits = 700) has returned an entry
for the Define Device Area (DDA) that has an invalid
value for the IOCN in the Define Device Structure
(DDS).
The loadlist processor will continue processing after
displaying the error.
Action: If the VRM minidisk has been changed by
adding additional code, remove the module that returned
the invalid DDA entry.
describes more
Section 5. Blinking Messages 5-11