This is an image of a graph. The x-axis is labeled "Undo Retention (minutes)". The y-axis is labeled "Required Tablespace Size (MB)". A curve starts roughly from the origin and climbs to the upper right, more or less linearly. The curve has tick-marks on it, which you can click. There are three points called out on the curve, listed here in order of proximity to the origin: Auto-Tuned Undo Retention, New, and Best Possible Undo Retention.