In an enhanced dynamic address translation facility a virtual address to be translated and an initial origin address of a translation table of the hierarchy of translation tables are used to access a segment table entry containing a format control field and an access validity field. If the format control field is enabled, the segment table entry further contains an access control field and a fetch protection field and a segment-frame absolute address. Fetch operations from the desired block of data are permitted if the program access key associated with the virtual address is equal to the segment access control field.