System, comprising an operator station client and an operator station server of a control system of a technical system and a controller optimisation module, wherein the operator station client is connected to the operator station server and is embodied: a) on the request of an operator of the control system, to retrieve trend data of a closed-loop control (10a, 10b) of the control system from a trend display service implemented on the operator station server continuously during runtime of the technical system, wherein the trend display server, via which a transfer of data from the operator station server to the operator station client takes place, is implemented within a visualisation service integrated in the operator station server, wherein the trend display service is embodied to retrieve the trend data from a process image of the operator station server and to transfer it to the operator station client, and display it on a display device of the operator station client in a first application environment that is implemented on the operator station client; b) to check the retrieved trend data as to whether at least one specific trigger criterion has been met; c) in the event of the at least one specific trigger criterion being met, to transfer a time range considered to be relevant in the trend data in the form of a subset of the trend data into a second second application environment that is displayed on the display device, is independent of the first application environment and is implemented on the operator station client; d) starting from the second application environment, to transfer the subset of the trend data transferred to the second application environment to the controller optimization module during runtime of the technical system, wherein the controller optimisation module is implemented on a separate server, which is independent from the operator station server and the operator station client, and on a separate computer infrastructure; e) to receive closed-loop control parameters revised by the controller optimization module using the received subset of the trend data, to store them in a data archive of the operator station server and to display them in the second application environment; f) to transfer the revised closed-loop control parameters from the second application environment to the first application environment; and g) to transfer the revised closed-loop control parameters to the closed-loop control (10a, 10b). a) on the request of an operator of the control system, to retrieve trend data of a closed-loop control (10a, 10b) of the control system from a trend display service implemented on the operator station server continuously during runtime of the technical system, wherein the trend display server, via which a transfer of data from the operator station server to the operator station client takes place, is implemented within a visualisation service integrated in the operator station server, wherein the trend display service is embodied to retrieve the trend data from a process image of the operator station server and to transfer it to the operator station client, and display it on a display device of the operator station client in a first application environment that is implemented on the operator station client; b) to check the retrieved trend data as to whether at least one specific trigger criterion has been met; c) in the event of the at least one specific trigger criterion being met, to transfer a time range considered to be relevant in the trend data in the form of a subset of the trend data into a second second application environment that is displayed on the display device, is independent of the first application environment and is implemented on the operator station client; d) starting from the second application environment, to transfer the subset of the trend data transferred to the second application environment to the controller optimization module during runtime of the technical system, wherein the controller optimisation module is implemented on a separate server, which is independent from the operator station server and the operator station client, and on a separate computer infrastructure; e) to receive closed-loop control parameters revised by the controller optimization module using the received subset of the trend data, to store them in a data archive of the operator station server and to display them in the second application environment; f) to transfer the revised closed-loop control parameters from the second application environment to the first application environment; and g) to transfer the revised closed-loop control parameters to the closed-loop control (10a, 10b).