You can use any of the
following items to assign a SAS libref:
A libref assignment
remains in effect for the duration of the SAS job, session, or process
unless you clear the libref or use the same libref in another LIBNAME
statement or LIBNAME function.
If you assign a libref
from a SAS process, that libref is valid only within that SAS process.
If you clear a libref from within a SAS process, that libref is not
cleared from other SAS processes.