Dynamic address translation with translation table entry format control for identifying format of the translation table entry

A system 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 system comprising:

• a computer memory capable of storing machine instructions and a hierarchy of translation tables used for dynamic address translation of a virtual address into a real address or absolute address of a desired block of data in said main storage, said real address being subject to a prefixing operation;
• and
• a processor in communication with said computer memory, said processor capable of accessing said hierarchy of translation tables stored in said memory, said processor performing a method comprising:
• based on an initial origin address of a translation table of a hierarchy of translation tables comprising a segment table, obtaining a segment table entry from said segment table, said segment table entry configured to include a format control field;
• based on an enhanced Dynamic Address Translation (DAT) facility being enabled, determining whether said format control field consists of an enabled value or a not-enabled value, wherein the enabled value of the format control field indicates the segment table entry is configured to consist of a first set of functional fields, a second set of functional fields and a segment-frame absolute address of a large block of main storage, wherein the not-enabled value of the format control field indicates the segment table entry is formatted to consist of the first set of functional fields and an origin address of a page table;
• and
• based on said determining said format control field is enabled, the processor performing:
• obtaining from said segment table entry, by the processor, said segment-frame absolute address of said large block of main storage;
• combining, by the processor, said 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, wherein the formed translated address consists of said segment-frame absolute address, said page index portion of said virtual address, and said byte index portion of said virtual address, wherein said desired block of main storage consists of one or more bytes of data;
• and
• accessing said desired block of main storage addressed by said translated virtual address.

A computer implemented method for translation in a computer system of a machine architecture having a CPU, a memory, and a hierarchy of translation tables used for translation of a virtual address into a translated address of a block of data in main storage, the method comprising:

• based on an initial origin address of a translation table of a hierarchy of translation tables comprising a segment table, obtaining a segment table entry from said segment table, said segment table entry configured to include a format control field;
• based on an enhanced Dynamic Address Translation (DAT) facility being enabled, determining whether said format control field consists of an enabled value or a not-enabled value, wherein the enabled value of the format control field indicates the segment table entry is configured to consist of a first set of functional fields, a second set of functional fields and a segment-frame absolute address of a large block of main storage, wherein the not-enabled value of the format control field indicates the segment table entry is formatted to consist of the first set of functional fields and an origin address of a page table;
• and
• based on said determining said format control field is enabled, a processor performing:
• obtaining from said segment table entry, by the processor, said segment-frame absolute address of said large block of main storage;
• combining, by the processor, said 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, wherein the formed translated address consists of said segment-frame absolute address, said page index portion of said virtual address, and said byte index portion of said virtual address, wherein said desired block of main storage consists of one or more bytes of data;
• and
• accessing said desired block of main storage addressed by said translated virtual address.