While the LIBRARY option is extremely helpful for relatively static data/ formats, and don't forget INFORMATS, the FMTSEARCH option controlling the order that libraries are searched for formats can be helpful when using data that is not always loaded. I work on many projects that have durations of a couple months and it is nice that I can add a projects formats to the search path so I don't have to come up with different format names such as gender when the active project has gender coded differently (and is sometimes critical as one project has 6 "genders" in addition to "not recorded" codes.

Don't forget the custom INFORMATS that can be created so you can read the data, or convert data, with the added advantage of other and _error_ options to provide invalid data notes in the log.

And multilabel formats are sometimes a very slick answer to some complicated report table layouts.