Each tile would be 180 degrees by 90 degrees as shown in Figure  2-3 . In this figure, each tile is 90 degrees by 45 degrees. The length refers to the length of the tile along the specified dimension. Thus, at level 2 the tiles are 90x45 degrees in size. As the number of levels increases, the tiles become smaller and smaller.
Smaller tiles provide a more precise fit of the tiles over the geometry being indexed.
However, because the number of tiles generated is unbounded, you must take into account the performance implications of using higher levels. See Chapter  6 for a description of this procedure. Data modeling is an important part any database design, and is essential in a spatial database where the data often represents actual physical locations. Increasing the level increases the number of tiles to provide a more precise fit of the tiles over the object. An implicit commit is not executed after the procedures are called.