1. A computer program product for translation of a virtual address into a translated address of a block of data in main storage in a computer system of a machine architecture, the computer program product comprising: a storage medium readable by said computer system, said computer readable medium storing instructions for performing: obtaining the virtual address to be translated; obtaining an initial origin address of a translation table of said hierarchy of translation tables, said hierarchy of translation tables comprising a segment table; based on the obtained initial origin, obtaining a segment table entry from said segment table, said segment table entry configured to contain a format control field; in response to an enhanced DAT facility being enabled, determining whether said format control field in said segment table entry is enabled; and in response to said format control field being enabled, performing: obtaining from said segment table entry a segment-frame absolute address of a large block of data in main storage, each 4K byte block of said large block of data having an associated storage key, each storage key comprising a change bit, wherein a translated address of a desired block of data within said large block of data in main storage comprise a combination of said segment-frame absolute address, a page index portion of said virtual address and a byte index portion of said virtual address, said desired block of data consisting of one or more bytes of data; determining whether a change recording override field in said segment table entry is enabled; performing a store operation associated with said virtual address to said desired block of data; and in response to said change recording override field being disabled, performing: setting said change bit of said storage key associated with said desired 4K block to 1; and indicating that said desired 4K block has been modified.