1. A computer program product for emulation by a native computer system of a native machine architecture, a translation of a virtual address into a translated address of a desired block of main storage of another computer system of another machine architecture, the computer program product comprising: a computer readable storage medium readable by said computer system, said computer storage medium storing instructions for performing a method comprising: based on receiving, by the native computer system, a virtual address of the another machine architecture, executing, by the native computer system program code to perform a method comprising: performing an address translation of a virtual address to obtain an address of a desired block of main storage, wherein the address translation is based on a translation table entry of a translation table, wherein the desired block of main storage has an associated change (C) field for indicating whether said block of main storage has been modified, the C field having a C value; based on the obtained address, initiating, by the computer system, a store operation to said desired block of main storage; and based on a change override (CO) field of the translation table entry having a first CO value, the store operation causing an associated C field to have a first C value, the first C value to indicate the block of main storage has been modified; and based on the CO field of the translation table entry having a second CO value, the store operation not changing the C value of the associated C field.