The reliability of a series system is inherently low. One of the methods employed to improve the reliability is to employ active redundancy. To maximize the system reliability without violating the constraints on the resources, the addition of redundant units should be cost-effective. The current highest value of the stage selection factor, which takes the cost
(resource consumption) indirectly, is taken as the basis to determine the stage where the addition of the next redundant unit would be highly cost-effective. Illustrative examples are provided and the success rate of the algorithm is found to be high.

If a system consists of n components, and if all the components are to be operative for the success of the system, then its Reliability Block Diagram (RBD) has to be modeled as a series configuration. (In the RBD, each component is shown as a block. It shows the logical connections among the various components). For a series configuration, the overall system reliability is the product of the component (sub-system) reliabilities, each of which is less than unity. Hence, the reliability of a series system is inherently low. One of the methods of improving the reliability is to employ active redundancy. While any degree of reliability can be achieved by employing the requisite number of redundant units, the availability of the resources may pose a problem. Hence, it becomes necessary to obtain the maximum possible reliability, without violating any one of the given constraints. Though the redundancy optimization problem may be solved by the conventional methods, yet, the integer solution requirement may necessitate the rounding off of the true
optimal values. Hence, the reliability obtained is not the true optimal reliability, but the nearest possible one.

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