Since you submitted to Corbel, I thought you might find the followin from Sungard Corbell's Adoption Agrement Guide interesting.
"This option permits partial withdrawals only for required minimum distributions under Code Section 409(a)(9). This option should be selected if the only other form of distribution permitted under the plan is a lump sum and the employer wants to permit participants who arer subject to required minimum distributions to be able to take out more than just the minimum distribution but not the entire amount."