Using large pages

A large page, or a 1–megabyte page, is a special-purpose performance feature for memory objects. To request large pages for backing the memory object, authorized programs and unauthorized programs with read authority to facility class IARRSM.LRGPAGES can specify the PAGEFRAMESIZE parameter when issuing the IARV64 GETSTOR macro. Authorized programs can also request large pages for common memory objects by using PAGEFRAMESIZE when issuing the IARV64 GETCOMMON macro.

Large pages consume real storage and are non-pageable. The system programmer should carefully consider what applications are granted access to large pages. The key factors to consider when granting access to large pages are as follows:

Memory usage
Page translation overhead for the workload
Available large frame area

Long-running memory-intensive applications benefit most from using large pages. Short-lived processes with a small memory working set are not good candidates. The system programmer defines the amount of real storage that can be used for large pages with the LFAREA system parameter. See IEASYSxx description in z/OS MVS Initialization and Tuning Reference.