I am using a SELECT query on a database table. Since the number of records in the table is very large

In this case you could use the PACKAGE SIZE addition in the SELECT query to process in limited amount of data, thus avoiding the memory overloads.

Eg:

SELECT *
FROM
INTO TABLE itab
PACKAGE SIZE .

IF sy-subrc EQ 0.
*" Process the n records
ENDIF.

ENDSELECT.