Independent overflow part

The independent overflow part contains empty CIs that can be used by any UOW in the area.

When a UOW gets a CI from the independent overflow part, the CI can be used only by that UOW. A CI in the independent overflow part can be considered an extension of the overflow section in the root addressable part as soon as it is allocated to a UOW. The independent overflow CI remains allocated to a specific UOW unless, after a reorganization, it is no longer required, at which time it is freed.