Root segment

The most desirable block depends on the access method.

For HDAM or PHDAM roots, the most desirable block is the one containing either the RAP or root segment that will point to the root being inserted. For HIDAM or PHIDAM roots, if the root does not have a twin backward pointer, the most desirable block is the one containing the root with the next higher key. If the root has a twin backward pointer, the most desirable block is the root with the next lower key.