When is taking an oath (breaking it) unlawful, reprehensible, obligatory, or recommended?

An oath is forbidden if it is taken to commit a prohibited act, or by something that is impermissible to swear by. It is disliked if it is frequent, or if it is taken to commit a disliked act, or to abandon a recommended one. It becomes obligatory if an obligation depends on it, and recommended if it is for the realization of a benefit. An oath is categorized into obligatory, recommended, permissible, disliked, and forbidden.