z/VSE's virtual and real storage support
Ingolf24 120000DRN3 Visits (2552)
Last week there was a question on z/VSE's real storage support on VSE-L. Therefore I think it's worth to have a blog entry for virtual and real storage support in z/VSE.
Virtual storage defined by VSIZE of the IPL Supervisor parameter command is used by private areas, shared areas, data spaces and memory objects. The private area is the space between the end of the Shared Virtual Area (SVA 24 bit), up to the beginning of the Shared Virtual Area (SVA 31-bit). z/VSE partitions are usually allocated in the private area. The private area also includes private (64 bit) memory objects, if allocated. Shared areas are shared among all address spaces and include the Supervisor, all shared areas (SVA 24 bit, SVA 31 bit) as well as shared memory objects, if allocated. Data spaces can be defined by programs and for virtual disks. Data spaces and memory objects can only hold data. Memory objects are contiguous ranges of virtual storage that are allocated by programs.
The maximum value of virtual storage (VSIZE) that z/VSE can support is about 90 GB. However, the actual usable VSIZE on your z/VSE system depends on the size of the processor (real) storage, the capacity of your page data set devices, the type of your workload, the system setup, the processor capacity, ... If VSIZE "fits" into the real storage you may run without a page data set. z/VSE can support a maximum of 32 GB of real storage. If you have more real storage available than you need for your workload, you may consider to add virtual disks to improve I/O performance for temporary files or libraries. See my blog entry on virtual disk.
You can get more information or z/VSE's storage support in the z/VSE Planning book. Our documentation is here.