No. The cylinders themselves extended into the crankcase and stuck up above the floor of the case about an inch so that oil didn't run into the cylinders. The only oil that fell into the cylinder was that which dripped off the crankshaft after shutdown, and it wasn't enough to fill the piston to the point that it ran through the oil ring groove drain holes and down past the compression rings into the combustion chamber. Hydraulic lock was never an issue with the DB's or the Jumo's. However there was another issue with the DB 600 series; it was very difficult to obtain consistent oil consumption since the rotation of the crankshaft one cylinder bank got more oil than the other. This increased oil consumption on one cylinder bank and reduced the anti-knock value of the fuel/air charge. For this reason the engine was built with different cylinder compression ratios on the two cylinder banks.
