Edit to spec as necessary:
DELIMITER $$
CREATE PROCEDURE trimTable()
BEGIN
DECLARE ROWS INT;
DECLARE rows_deleted INT;
SET ROWS = 1;
SET rows_deleted = 10000;
WHILE ROWS > 0
DO
DELETE FROM db.tabA WHERE predicate_col < CURDATE() - INTERVAL 90 DAY ORDER BY `id` LIMIT 10000;
SET ROWS = ROW_COUNT();
SET rows_deleted = rows_deleted + ROW_COUNT();
SELECT rows_deleted AS "Rows Deleted";
END WHILE;
END $$
DELIMITER ;