Something like this should do the trick:
—* FIND THE ROWS IN TABLE TTESTA THAT HAVE NO MATCH IN TTESTB
SELECT COL1, COL2
FROM TTESTA TA
WHERE NOT EXISTS (SELECT 1
FROM TTESTB TB
WHERE TA.COL1 = TB.COL1
AND TA.COL2 = TB.COL2)
An outer join could also be used.
If you could match the data using only the Primary Key, it would run faster because it would only need to use the indices. Are you sure you need to match every column?