DELETE VARIABLES var_list.
DELETE VARIABLES deletes the specified variables from the
dictionary. It may not be used to delete all variables from the
NEW FILE to do that (see NEW FILE).
DELETE VARIABLES should not be used after defining transformations
but before executing a procedure. If it is used in such a context, it
causes the data to be read. If it is used while
TEMPORARY is in
effect, it causes the temporary transformations to become permanent.