Real regions begin at the top of the system region (see Figure 1) and are allocated upward to the bottom of the area containing LSQA, SWA, and the user key area (subpools 229, 230, and 249). Unlike virtual regions, real regions are only allocated below 16 megabytes.

The system assigns real regions to a virtual space within the private area that maps one-for-one with the real addresses in central storage below 16 megabytes. Central storage for the entire region is allocated and fixed when the region is first created.