The IARR2V macro provides a simple method to obtain a virtual storage address from a central storage address. This conversion can be useful, for example, when you are working with an I/O or diagnostic program that provides central storage addresses, but you want to use virtual storage addresses.
The details of the syntax and parameters of IARR2V are in z/OS MVS Programming: Authorized Assembler Services Reference EDT-IXG. In its simplest form, the IARR2V macro requires only the RSA parameter. The RSA parameter specifies the central storage address that you want to convert.
The system returns the virtual storage address in a register or in a storage location you specify through the VSA parameter. Also, you can request the system to return the ASID or STOKEN of the address space or data space associated with the address. For an authorized program, you may also specify the type of linkage the system is to use.
If you require knowledge of whether the central storage address you have is being shared through the IARVSERV macro, you can get that information using the WORKREG, NUMVIEW, and NUMVALID parameters. To use the NUMVIEW and NUMVALID parameters, you must use the WORKREG parameter to specify the work register for the system to use. The NUMVIEW parameter requests the total number of pages sharing the view of your central storage address. NUMVALID requests the number of pages currently addressable (accessed), which is called the number of valid views. With NUMVIEW and NUMVALID, you can check how effectively programs are using shared storage. Pages that are not accessed have not been read or updated by any program.