This is a manual that was unavailable for several years, but without
any fanfare IBM seems to have resurrected it.

http://publibfi.boulder.ibm.com/epubs/pdf/25119200.pdf

It is my experience that former Pickies found this very useful and
seemed to reference it more than any other.

As a Primate, I said ho-hum, but the Pickies I've known preferred this
book over the rest.

cds

P.S.

This is the only place I know where UniVerse's implementation of
U-conversion codes for "User Exits" is adequately documented.