Method, apparatus and computer usable medium tangibly embodying a program of instructions is provided for performing advanced cost/benefit analysis of subplans of a query execution plan, in a computer system having a database software server. Method augments a cost estimation model, obtained from an optimizer of the software server after determination of an optimal query execution plan, with a cost/benefit analysis of operating each subplan of the query execution plan asynchronously. It calculates a subplan elapsed time benefit of making the subplan asynchronous using a set of cost estimates for each subplan operation and knowledge of the execution sequence of the query execution plan operations, all provided by the query optimizer. Set of subplans for asynchronous execution is chosen to form an optimal set of subplans while respecting a resource constraint, for providing a maximal reduction of the total query elapsed time while conserving system resources of the software server.