1. A computer program product for protecting data 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 a virtual address of a desired block of main storage to be translated; obtaining an initial origin address of a translation table of a hierarchy of translation tables, said hierarchy of translation tables comprising a segment table; based on the obtained initial origin address and the obtained virtual address, performing a dynamic address translation to obtain a segment table entry from said segment table, said segment table entry configured to contain a format control field, said format control field, when enabled indicating the segment table entry consists of a first format of fields, said format control field when not-enabled, indicating the segment table entry consists of a second format of fields, the first format of fields including a dynamic address translation (DAT) protection field (P), the second format of fields absent the DAT protection field; in response to an enhanced dynamic address translation (eDAT) facility being enabled, wherein translation table entries of the hierarchy of translation tables used in said dynamic address translation, other than the segment table entry, comprise DAT protection fields, 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 main storage and a first DAT protection field; combining said obtained segment-frame absolute address with a page index portion of said virtual address and a byte index portion of said virtual address to form the translated address of the desired block of main storage within said large block of main storage, said desired block of main storage consisting of one or more bytes of data; determining whether any DAT protection fields in any translation table entries used in said performed dynamic address translation of said virtual address are enabled; and in response to all of said DAT protection fields being not enabled, permitting store operations to said desired block of main storage in response to said store operations being associated with said performed address translation.