Method for configuring a system for monitoring the performance of a control loop of an industrial plant, including the steps • reading in first process data (p1_i, p_i) derived from measurements of at least one sensor inside the control loop during a particular control situation, • calculating from the first process data a corresponding at least one performance index (l1, l, l_n) indicating the behaviour of the control loop, • determining a first quality of the control performance depending on the difference between the at least one performance index and a corresponding threshold value (T1, T, T_n), characterized in that • in case that the first quality of the control performance is determined to be less than good, a second quality of the control performance is determined ∘ either by calculating the second quality from an analysis of second process data (p2_i) derived in a different way from measurements of the at least one sensor or of at least one further sensor inside the control loop during the same particular control situation, ∘ or by processing an input (Inp) from a user of the system which indicates the second quality, • if the second quality is also less than good, the first quality is regarded to be confirmed and correct and the method ends, • if the second quality of the control performance is determined to be good or better, the at least one threshold value (T1, T, T_n) is adjusted to have a value close to the at least one performance index (l1, l, l_n), • in the next step, the first quality is calculated again, where it is now expected that the first quality should have the same level as the second quality, • if the first quality is better than good, as expected, the at least one adjusted threshold value is stored permanently in order to be available for the next time the control performance diagnosis is performed, and then the method ends successfully, • if, in the alternative, the first quality is still less than good, the method ends with an appropriate error message. • reading in first process data (p1_i, p_i) derived from measurements of at least one sensor inside the control loop during a particular control situation, • calculating from the first process data a corresponding at least one performance index (l1, l, l_n) indicating the behaviour of the control loop, • determining a first quality of the control performance depending on the difference between the at least one performance index and a corresponding threshold value (T1, T, T_n), • in case that the first quality of the control performance is determined to be less than good, a second quality of the control performance is determined ∘ either by calculating the second quality from an analysis of second process data (p2_i) derived in a different way from measurements of the at least one sensor or of at least one further sensor inside the control loop during the same particular control situation, ∘ or by processing an input (Inp) from a user of the system which indicates the second quality, ∘ either by calculating the second quality from an analysis of second process data (p2_i) derived in a different way from measurements of the at least one sensor or of at least one further sensor inside the control loop during the same particular control situation, ∘ or by processing an input (Inp) from a user of the system which indicates the second quality, • if the second quality is also less than good, the first quality is regarded to be confirmed and correct and the method ends, • if the second quality of the control performance is determined to be good or better, the at least one threshold value (T1, T, T_n) is adjusted to have a value close to the at least one performance index (l1, l, l_n), • in the next step, the first quality is calculated again, where it is now expected that the first quality should have the same level as the second quality, • if the first quality is better than good, as expected, the at least one adjusted threshold value is stored permanently in order to be available for the next time the control performance diagnosis is performed, and then the method ends successfully, • if, in the alternative, the first quality is still less than good, the method ends with an appropriate error message.