I meant to clarify one other point as well. "Keep" is not a function. It is either a data set option, or a data set statement.
I'm going to be fussy about that because I want to comment that reading the Online help is wonderfully helpful, but because it is screen based it is often harder to do than flipping through the printed manual. While the structures largely mirror each other, I can find something in a manual faster than I can online. Part of that is because I used them for so long that the structure and hierarchy of the chapters are almost second nature. On that basis, looking up KEEP in the functions part of the reference will have you looking in the wrong place.
Incidentally, while the word search part of the online help is supposed to find these words quickly, I usually find the result set that is returned is too large and it is more of a hindrance. If I had any suggestion on how to do it otherwise, I'd tell the SAS Docs people, but I don't know. So I stick with my tried and trusted approach of viewing the online docs as a series of books and "virtually flick through" the chapters to get where I want. Now if I could only make bookmarking work for me!!!
Kind regards
David