Round robin works with a fixed amount of data, and a pointer to the current element. This can be described like a circle with N dots plotted on the edge of the circle. Those dots are the places where data can be stored. The pointer can be described like an arrow from the center of the circle to one of the dots. It shows to the current dot. When the current data is read or written, the pointer moves to the next element. As we are on a circle there is no beginning nor an end, you can go on and on. After a while, all the available places will be used and the process automatically reuses old locations. It is easy to understand that this database will not grow and the file size is always the same.