SQL & PL/SQL

I have to load around 20 million rows from SQL Server table to Oracle table using Network Link,wrote following code using Bulk Collect,which is working but taking more time(taking 5 hrs).
I also tried with changing table to parallel degree 8 didn't help(Also Oracle Table set to NOLOGGONG mode).
Is there any better way to do this ? Appreciate any help in this regard .

Script :
CREATE OR REPLACE PROCEDURE INSERT_SQLSERVER_TO_ORACLE
IS
TYPE v_ARRAY IS TABLE OF TARGET_CUST%ROWTYPE INDEX BY BINARY_INTEGER;
ins_rows v_ARRAY;
BEGIN
DECLARE CURSOR REC1 IS
SELECT COL1, COL2,COL3,COL4 SOURCE_SQLSERVER_CUST;
BEGIN
OPEN REC1;
LOOP
FETCH REC1 BULK COLLECT INTO ins_rows LIMIT 5000;
FORALL i IN ins_rows.FIRST..ins_rows.LAST
INSERT INTO TARGET_CUST VALUES ins_rows(i);
EXIT WHEN REC1%NOTFOUND;
END LOOP;
COMMIT;
CLOSE REC1;
END;
END;



Thanks in Advance.