We propose an efficient and effective heuristic algorithm for dynamic reconfiguration of virtual topology in an Optical WDM network. Heuristic uses a basic and promising approach to achieve optimal virtual topology. In previous studies, the objectives of reconfiguration are to minimize the load of the maximally loaded lightpath or average weighted hop distance, or to provide load balancing. In order to achieve minimization of the load on the maximally loaded lightpath, our algorithm tears down lightpaths without increasing the load on the maximally loaded lightpath. Then, it sets up lightpaths in order to decrease the load of the maximally loaded lightpath. The advantages of our algorithm are: It does not need to know the future traffic pattern. Its complexity is low so that it can be run online. Moreover the network administrator can decide how much the network will be interrupted. The optimization objective is achieved as tested in the simulations.