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![]() A comparison of data reference in primary and AR mode z/OS MVS Programming: Extended Addressability Guide SA23-1394-00 |
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The best way to show how address resolution in primary mode compares with address resolution in AR mode is through an example. Figure 1 and Figure 2 show two ways an MVC instruction works to move data at location B to location A. In Figure 1, the move instruction, MVC, is in code that is running in primary mode. The MVC instruction uses GPRs 1 and 2. GPR 1 is used as a base register to locate the destination of the MVC instruction. GPR 2 is used as a base register to locate some data to be moved. Figure 1. The MVC instruction in primary mode
![]() In Figure 2, the MVC instruction, in code that is in AR mode, moves the data at location B in Space Y to location A in Space X. GPR 1 is used as a base register to locate the destination of the data, and AR 1 is used to identify space X. GPR 2 is used to locate the source of the data, and AR 2 identifies Space Y. In AR mode, the MVC instruction is in code that is running in AR mode. The MVC instruction moves data from one address/data space to another. Note that the address space that contains the MVC instruction does not have to be either Space X or Space Y. Figure 2. The MVC Instruction in AR Mode
![]() Addresses that are qualified by an ALET are called ALET-qualified addresses. ![]() ![]() ![]() |
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