ILOG CPLEX provides the DataCheck parameter to check the correctness of data used in problem creation and problem modification methods. When this parameter is set, ILOG CPLEX will perform extra checks to determine that array arguments contain valid values, such as indices within range, no duplicate entries, valid row sense indicators and valid numerical values. These checks can be very useful during development, but are probably too costly for deployed applications. The checks are similar to but not as extensive as those performed by the CPXcheckData functions provided for the C-API. When the parameter is not set (the default), only simple error checks are performed, for example, checking for the existence of the environment.