1. A method for protecting data in a computer system having a hierarchy of translation tables used for translation of a virtual address into a translated address of a block of main storage, the method comprising: building a software routine to emulate execution of an instruction of a first computer architecture on a general purpose processor of an alternate computer architecture, the instruction configured to protect data, the software routine comprising a plurality of instructions, the software routine configured to cause the general purpose processor of the alternate computer architecture to perform a method comprising obtaining for translation a virtual address of a desired block of main storage; obtaining an initial origin of a translation table in a hierarchy of translation tables, said hierarchy of translation tables comprising a segment table; based on said obtained initial origin address and said virtual address, obtaining a segment table entry from said segment table, said segment table entry configured to contain a format control field; based on an enhanced dynamic address translation (eDAT) facility being enabled, determining, by a processor, whether said format control field in said segment table entry is enabled; and based on said format control field being enabled, performing: determining whether an access validity field in said segment table entry is enabled, said segment table entry comprising said access validity field, a segment access control field, a segment fetch protection field and a segment-frame absolute address of a large block of main storage, said large block of main storage comprising said desired block of main storage; and based on said access validity field being enabled, performing: permitting stores to said desired block of storage, wherein the stores are associated with the virtual address, said stores permitted in response to said segment access control field matching a program access key provided by any one of a Program Status Word or an operand of a program instruction being executed, wherein the stores are associated with the virtual address; and not permitting stores to said desired block of main storage based on said segment access control filed not matching said program access key, wherein the stores are associated with the virtual address.