If you assign noncritical objects to a segment, those objects cannot grow beyond the space available in the segment’s devices. Conversely, if you assign a critical table to a segment, and the segment’s devices are not available to other segments, no other objects will compete with that table for space.
When the devices in a segment become full, you can extend the segment to include additional devices or device fragments as needed. Segments also allow you to use thresholds to warn you when space becomes low on a particular database segment.
If you create additional segments for data, you can create new threshold procedures for each segment. See Chapter 29, “Managing Free Space with Thresholds,” for more information on thresholds.