The Economic Order Quantity (EOQ) zone is beneficial for giving some latitude in picking the lot sizes in a continuous time inventory problem, but it is not suitable for a discrete time inventory problem, the discrete lot sizing (DLS) problem. In this paper, a novel enumeration method is proposed and coded as a user-friendly computerized scheduling system to "visualize" the complex DLS problems by projecting the entire feasible solutions on a two dimension space, where setup frequency and total cost are placed on the horizontal and the vertical axis respectively. First, the zone around the optimal solution in the DLS problem is demonstrated always smooth and this phenomenon is defined as DLS zone in which giving a small penalty cost from the optimal solution brings several alternative solutions for picking the lot sizes. Second, even if the penalty costs are changed, the computerized scheduling system is able to determine the adaptive decision zone and find the included alternative solutions. The flexibility in picking the lot sizes for discrete time inventory problems is significantly enhanced since decision makers are enabled to choose a preferable solution from the DLS zone. (C) 2010 Elsevier Ltd. All rights reserved.