From the MVS extended Addressability Manual …SA22-7618-08
A subspace is a specific range of storage in the private area of an address space, designed to limit the storage a program can reference. A program that is associated with a subspace cannot reference some of the private area storage outside of the subspace storage range; the storage is protected from the program. Whether a given range of private area storage is protected from a program associated with a subspace depends on whether the storage is: Eligible to be assigned to a subspace (or “subspace-eligible”) Assigned to a subspace Not eligible to be assigned to a subspace. You control these storage “states” through the IARSUBSP macro. Storage outside of the private area is not affected by subspaces. A program running in an address space can reference all of the storage associated with that address space. In this section, a program's ability to reference all of the storage associated with an address space is called full address space addressability. A program running with full address space addressability can reference storage in any of the three states: eligible to be assigned to a subspace, assigned to a subspace, or not eligible to be assigned to a subspace. A program that runs in an address space that owns subspaces also has full address space addressability. While running in a subspace, a program now has access to 64-bit private and shared storage. It can reference the 64-bit storage while in subspace mode and no longer needs to issue the BSG (Branch in Subspace Group) instruction to switch to the base mode to reference the 64-bit storage. A program running in a subspace can reference storage that is assigned to its own subspace and storage that is not eligible to be assigned to a subspace. It cannot reference storage that is eligible to be assigned to a subspace or storage that is assigned to a subspace other than the one in which the program is running. In other words, a subspace allows a program running in it to reference all of the storage associated with the address space except the private area storage that is eligible to be assigned to a subspace or assigned to another subspace. When storage is not eligible to be assigned to a subspace and not assigned to a subspace, it can be referenced by a program running in a subspace or a program running with full address space addressability. This storage can be referenced by all subspaces as well as by programs running with full address space addressability. An address space that owns subspaces is also called a “base space”. Figure 74 illustrates the concept of creating a subspace in base space ASID 23. From: [email protected] Sent: Wednesday, May 14, 2014 9:09 AM To: IBM Mainframe Discussion List On Wed, May 14, 2014 at 7:47 AM, Shane Ginnane <[email protected]> wrote: > On Wed, 14 May 2014 06:50:09 -0500, John McKown wrote: > > >I've never heard of "Sub Address Space" storage. I can't figure out what > >you mean. > > Try subspace group. > I have some minimal knowledge of that, thanks to CICS using them. But I don't see where that has much to do with STORAGE OBTAIN, other than complicating things when storage needs to be shared between an key 8 and a key 9 program. I think that IBM is missing out on a possibility, due to TSO being moribund, of using a subspace group the way that CICS does in order to more securely separate the non-APF TSO commands from the APF authorized commands. Run them in separate subspace groups. I wonder what perversions I can get UNIX to perform using them? > > Shane ... > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- There is nothing more pleasant than traveling and meeting new people! Genghis Khan Maranatha! <>< John McKown ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
