one Level file name or two level file name.
libref is 1 to 8 characters long, begins with a letter or underscore, and contains only letters,
numbers, or underscores.
To reference a SAS file, you use a two-level name, libref.filename. In the two-level name, libref
is the name for the SAS library that contains the file, and filename is the name of the file itself. A
period separates the libref and filename.
To reference temporary SAS files, you specify the default libref Work, a period, and the filename.
Alternatively, you can simply use a one-level name (the filename only) to reference a file in a
temporary SAS library. Referencing a SAS file in any library except Work indicates that the SAS
file is stored permanently.
SAS data set names can be 1 to 32 characters long, must begin with a letter (A–Z, either
uppercase or lowercase) or an underscore (_), and can continue with any combination of
numbers, letters, or underscores.
SAS Variable can be 1 to 32 character long.