A printing system having a print bar on which are installed multiple printheads, wherein the printheads on the print bar are arranged in a page-wide array configuration, such that when installed the printheads cover substantially the whole width of a print zone in which printing can be performed, and wherein the print bar is positioned at a predetermined height above a substrate, the system comprising: a nozzle servicing module moveable across the length of the print bar to selectively perform a nozzle servicing operation on a group of printhead nozzles; a printhead carriage moveable parallel to the print bar and on which is installed an auxiliary printhead; and a controller to: move the nozzle servicing module from one end of the print bar to a position along the print bar to perform a nozzle servicing operation; move the printhead carriage in synchronization with the nozzle servicing module; and transfer, during a printing operation, printhead control data intended for printhead nozzles on the print bar obscured by the nozzle servicing module to corresponding nozzle circuits on the auxiliary printhead, and wherein the printing system is configured to perform a printing operation whilst the nozzle servicing module is performing a nozzle servicing operation on a printhead on the print bar, without interrupting the printing operation being performed, and wherein the nozzle servicing module is configured to perform a servicing operation on a group of printhead nozzles without modifying the height of the print bar, and wherein the controller is configured to replace printhead nozzles obscured by the nozzle servicing module by nozzles on the auxiliary printhead as the nozzle servicing module moves across the length of the print bar. a nozzle servicing module moveable across the length of the print bar to selectively perform a nozzle servicing operation on a group of printhead nozzles; a printhead carriage moveable parallel to the print bar and on which is installed an auxiliary printhead; and a controller to: move the nozzle servicing module from one end of the print bar to a position along the print bar to perform a nozzle servicing operation; move the printhead carriage in synchronization with the nozzle servicing module; and transfer, during a printing operation, printhead control data intended for printhead nozzles on the print bar obscured by the nozzle servicing module to corresponding nozzle circuits on the auxiliary printhead, and move the nozzle servicing module from one end of the print bar to a position along the print bar to perform a nozzle servicing operation; move the printhead carriage in synchronization with the nozzle servicing module; and transfer, during a printing operation, printhead control data intended for printhead nozzles on the print bar obscured by the nozzle servicing module to corresponding nozzle circuits on the auxiliary printhead, and wherein the printing system is configured to perform a printing operation whilst the nozzle servicing module is performing a nozzle servicing operation on a printhead on the print bar, without interrupting the printing operation being performed, and wherein the nozzle servicing module is configured to perform a servicing operation on a group of printhead nozzles without modifying the height of the print bar, and wherein the controller is configured to replace printhead nozzles obscured by the nozzle servicing module by nozzles on the auxiliary printhead as the nozzle servicing module moves across the length of the print bar.