This invention relates to a retractable and extendable awning and control system for automatically extending and retracting the awning. The swinging member is provided with a feeding member for transporting a medium which is fed from a medium feed section rotatably supported by the swinging member. For example, the mechanism may be used to limit the IO utilization of database applications in a shared computing system to a specified limit, and may apply RL techniques, along with domain-specific constraints, to the system to automatically control the rate of queries made by an application. When the pressure is reduce, the piston return to a normally closed position due to a biasing spring closing the servo lockout valve. In addition, a soil aeration apparatus may operate without a centrally disposed support shaft, thus enabling the tine-holder shafts to be positioned closer to one another and reducing the size of the apparatus.