Oracle Message ORA-12494 - cannot insert or delete a level, category, or release category

ERRORcannot insert or delete a level, category, or release category
CAUSEYou attempted to insert or delete a level, category, or release category definition.
ACTIONIf the label definition is no longer valid, change its name to one that identifies it as invalid.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.