As was explained in the previous chapter, to use Z buffering you must render with a rendering mode that has "ZB" in its name. However, Z buffering has more than a little effect on rendering performance. So when you are drawing background or otherwise do not need to use Z buffering, you should reset the rendering mode to one that disables the Z buffer.

Also, note that the RDP can hang up if you attempt to access the Z buffer when operating in Fill mode or Copy mode. For this reason, be sure to use the G_RM_NOOP rendering mode, which disables the Z buffer (along with the Blender itself), when in Fill mode or Copy mode.