Margherita
Some answers and some questions.
SAS Viya has the SPRE (SAS Platform Runtime Environment). So when using SAS Studio to run code, this is what you use, and in there you can use LIBNAME statements as you are used to from SAS9.
Applications like Visual Analytics use data from CAS libraries and as you write, the data has to be loaded into memory for those applications to work.
Tell us more about the use case, this will help us better understand your needs.
Thanks