Below is a collection of PROC APPEND SAS® papers. PROC APPEND is very useful when you need to append two or more datasets of the same structure. See also PROC SQL. See alternative PROC DATASETS and SET statement.
DELETE A; /* Best Practice to first delete dataset A */
/* Similar to SET A B in DATA Step */
PROC APPEND BASE = A /* Generally new dataset name without any content */
DATA = B /* Add dataset B records to the end of dataset A recods */
FORCE; /* Forces the records to join even if variable lengths differ */
SAS® Reference PROC APPEND Syntax