Creating and using data spaces

A data space is a range of up to two gigabytes of contiguous virtual storage addresses that a program can directly manipulate through assembler instructions. Unlike an address space, a data space contains only data; it does not contain common areas or system data or programs. Program code does not execute in a data space, although a program can reside in a data space as nonexecutable code.

The DSPSERV macro with the TYPE=BASIC parameter (the default) manages data spaces. Use this macro to:

Create a data space
Release an area in a data space
Delete a data space
Expand the amount of storage in a data space currently available to a program.
Load an area of a data space into central storage
Page an area of a data space from central storage

A program's ability to create, delete, and access data spaces depends on whether it is a problem state program with PSW key 8 - F, a supervisor state program, or a PSW key 0-7 program. All programs can create, access, and delete the data spaces they own or created, and can share their data spaces with other programs running in the same address space. In addition, supervisor state or PSW key 0-7 programs can share their data spaces with programs in other address spaces. Unless otherwise stated, this section describes what the supervisor state or PSW key 0-7 programs can do.

Use this section to help you create, use, and delete data spaces. In addition, four sources of information can help you understand how to use data spaces:

An introduction to extended addressability can help you verify that a data space, rather than a hiperspace would be the best choice for your program. See Basic decision: data space or hiperspace.
Using access registers, contains many examples of setting up addressability to data spaces.
One of the following contains the syntax and parameter descriptions for the macros that are mentioned in this chapter:
Principles of Operation contains descriptions of how to use the instructions that manipulate access registers.