Oracle Message ORA-12495 - cannot disable an enabled level, category, or release category

ERRORcannot disable an enabled level, category, or release category
CAUSEYou attempted to disable a level, category, or release category that had previously been enabled. An enabled label definition may be exist in some database label, so cannot be disabled.
ACTIONIf the label definition is no longer valid, change its name to one that identifies it as invalid. When any labels are converted to character strings, the new label definition will be used.