The function ora-lob-internal-lob-p returns whether it is internal (that is BLOB, CLOB or NCLOB) or not (that is BFILE or CFILE). The function ora-lob-element-type returns the LISP element type that best corresponds to the LOB locator. This will be one of
for BLOB and BFILE, or
for CLOB, NCLOB and CFILE, depending on the charset of the LOB object.
It is possible to distinguish between CLOB and NCLOB by looking at the result of ora-lob-char-set-form. It returns 2 for NCLOB and 1 for CLOB.
LispWorks User Guide and Reference Manual - 21 Dec 2011