Support for 64-bit virtual storage addresses
z/Series architecture supports the use of 64-bit registers and switching between
31-bit and 64-bit addressing modes. z/OS 1.2 introduced support for requesting
64-bit virtual storage, as well as controls on the use of storage "above the bar"
via the MEMLIMIT JCL parameter and new facilities in the IEFUSI user exit.
SDSF on z/OS reports the MEMLIMIT setting for active jobs and this information is
also retained in SMF type 30 records.
The IARV64 macro, introduced with z/OS 1.2, supports managing 64-bit memory objects
from programs running in 31 or 64-bit addressing mode.