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NNC-00423:

invalid data item syntax code string
Cause: A caller has provided an invalid data type code to the name server program interface.
Action: Not normally visible to the user, except when using the name server control program. If the error occurs when using the control program, retry the failing operation with a valid type name. Otherwise, turn on tracing and re-execute the failing operation. If the error persists, contact Worldwide Customer Support.