Data-in-virtual enables you to map data into virtual storage but deal only with the portion of it that you need. The DIV macro provides the system services that manage the data object. It enables you to map the object into virtual storage, create a window, and view through that window only the portion of the data object that you need. The system brings into central storage only the data that you actually reference.

You can map a data-in-virtual object in either an address space, a data space, or a hiperspace. Mapping the object into a data space or hiperspace provides additional storage for the data; the size of the window is no longer restricted to the space available in an address space. It also provides additional isolation and integrity for the data, as well as more direct methods of sharing access to that data.

Data-in-virtual is most useful for applications, such as graphics, that require large amounts of data but normally reference only small portions of that data at any given time. It requires that the source of the object be a VSAM linear data set on DASD (a permanent object) or a hiperspace (a temporary object).

Data-in-virtual is also useful for applications that require small amounts of data; data-in-virtual simplifies the way you access data by avoiding the complexities of access methods.

Technical description

See Data-in-Virtual in z/OS MVS Programming: Assembler Services Guide.