Suction Line Oil Level

I borrowed this topic from the H & P Forum but I have seen some discussion about my posts:

If positive displacement pump is running and stopped , pump is mounted on tank and suction length above oil level is 200 mm and there is no leakage in suction line and suction chamber ,whether the oil will remain full in suction line after pump stoppage . Will it fall down ?

What happens if length is 400 mm, 800 mm, etc.