There are two types of user regions: virtual (or V=V) and real (or V=R). Virtual and real regions are mutually exclusive; private areas can be assigned to V=R or V=V, but not to both. The installation determines the region to which jobs are assigned. Usually, V=R should be assigned to regions containing jobs that cannot run in the V=V environment, or that are not readily adaptable to it. Programs that require a one-to-one mapping from virtual to central storage, such as program control interruption (PCI) driven channel programs, are candidates for real regions.

For virtual regions, which are pageable and swappable, the system allocates only as many central storage frames as are needed to store the paged-in portion of the job (plus its LSQA). The processor translates the virtual addresses of programs running in virtual regions to locate their central storage equivalent.

For real regions, which are nonpageable and nonswappable, the system allocates and fixes as many central storage frames as are needed to contain the entire user region. The virtual addresses for real regions map one-for-one with central storage addresses.