The University of Kentucky, Lexington
Updates for VM/XA SP CMS 5.5 (1989-1990)

Using CMS 5.5 and VM/XA SP (5 May 1989)

CMS 5.5 is a significantly new and different CMS. There are new commands and new options, but the biggest changes are internal and aren't immediately obvious.

Extended Architecture

The traditional 370 architecture allowed only 24 bits for storage addressing, limiting programs to a 16 megabyte address space. The new extended architecture (XA) uses 31 bits for storage addressing, providing a potential for billions of bytes of addressability. (Note that VM/XA SP has an implementation limit of 999 megabytes and each userid has an assigned limit which generally is lower still.) In addition to this, XA introduces many other changes, most significantly in the input/output system and the format and use of reserved storage locations, control registers, and status indications.

VM/XA SP Release 2

VM/XA SP makes the new features of XA available to CMS and programs running under it. XA SP supports two modes of virtual machine operation: 370 and XA. In 370 mode (the initial setting at logon) the old 370 architecture and its constraints obtain. This has the benefit of increasing compatibility with previous releases of VM, but restricts programs to 16 megabytes. In XA mode all of the new features of XA are used, but at the cost of compatibility. The important point to remember here is that if you don't need a larger virtual machine you should keep below 16 megabytes and run in 370 mode to minimize your difficulties during conversion. The STORAGE command automatically handles mode switching as necessary based on your machine size.

VM/XA SP introduces a number of other changes that are unrelated to the new architecture. Changes in the spool system are perhaps the most obvious. There have been changes in the syntax of some commands and in the formats of many messages.

VM/XA SP does not yet provide all of features of earlier, non-XA versions of VM.

CMS Storage

CMS uses the address space from about 12 megabytes to 16 megabytes for its nucleus, disk directories, and shared code. This is true regardless of the size of your virtual machine. Thus a 12 megabyte machine provides about the same amount of space for user programs and data as a 16 megabyte machine. The initial storage size for most users at logon is 2 megabytes.


The current VS FORTRAN (2.3) is supported under XA SP. Large arrays that will extended above the 16 megabyte boundary must be declared in dynamic common. If these arrays are passed through to subroutines through the calling sequences then only the calling program needs to declare them as dynamic common.

Conversion Continues

In general, IBM-supplied commands work in all modes. Most other commands work in 370 mode (16 megabytes or less), but may not in XA mode (greater than 16 megabytes). Commands that haven't been converted will often fail with "operation exception" or "specification exception" errors. The chart below lists the status of some often-used commands.

Some of these commands are used by other commands. Many other commands, for example, depend on MENUEXEC for display management and are therefore not XA capable either.


  • Use storage under 12 megabytes whenever possible.
  • Use the STORAGE command to define your storage size and machine mode.
  • If you need a function that isn't supported in XA mode switch back to 370 mode by defining a storage size less than 12 megabytes.
  • Other Notes

  • The number of simultaneous users of the SESSION command is severely restricted under VM/XA.
  • The CMS Batch system is considerably different than the system used under HPO. The functions provided are about the same, but batch jobs must be written as EXECs. The syntax of the BATCH command has changed too. HELP NEWBATCH for more information.
  • To avoid a problem with the loader in virtual machines greater than 16 megabytes the EXECs used to load and execute programs (VSF2CG, for example) specify RMODE 24.
  • Conversion Status

    The following lists the status of the commands that are not supplied by IBM as a part of CMS (most were written here, at other universities, or are from non-IBM commercial sources). XA indicates that a command can be used in an XA-mode machine, 370 indicates that a 370-mode machine is required, No indicates that it is not available under VM/XA SP, and ? indicates a command that hasn't been tested.
    A-DISK      XA            HASM        XA            RAP         No
    ACCEPT      XA            I-DEAS      No            RATES       No
    Ada (IBM)   370           IEFBR14     XA            RBROWSE     370
    APRINT      370           INPUT       XA            RDRCOST     ?
    ASMXC       XA            INSTNAME    XA            REPRINT     ?
    ASMXCG      XA            IUCVTRAP    370           RESTART     XA
    ASMXG       XA            JES         XA            RESTORE     See PRESERVE
    AUTOLINK    XA            JOBS        XA            RETCODE     XA
    BALANCE     No            JULIAN      XA            REXXCALL    XA
    BASIC (OS)  No            KERMIT      No            REXXDUMP    XA
    BASIC (VS)  370           LABELS      ?             RSCAN       ?
    BATCH (New) XA            LEDIT       370           RUNID       ?
    BATCHSYS    XA            Librarian   ?             RXEDIT      ?
    BIGFILES    XA            LINEMODE    370           RXUNPACK    ?
    BROWSE      XA            LINKS       XA            SADT        ?
    BURN        XA            LISP        ?             SCAN        ?
    C (IBM)     XA            Lisp (IBM)  XA            Scratchpad  370
    CADAM       No            LISTX       370           SCRIPT      370
    CALC        XA            LOOK        XA            SEARCH      370
    CALENDAR    370           LWBADGE     ?             SELECT      370
    CANCEL      XA            LWDEST      XA            SENDGATE    ?
    CASE        XA            LWGDDM      370           SESSION     370
    CATIA       No            LWNAMES     XA            SET7171     370
    CBDS        No            LWPLOT      370           SHIP        XA
    CC          No            LWPRINT     XA            Simscript   ?
    CHECKBUF    XA            LWSCRIPT    ?             SLFTEACH    ?
    CJSPREP     ?             MAIL        XA            SORTF       370
    CLRSCRN     XA            MAILBOOK    XA            SPACE       XA
    CMSCMSG     No            MAILCHEC    XA            SPELL       370
    CMSDIO      No            MANUAL      370           SPELLCHK    370
    CMSEMSG     No            MATCH       XA            SPELLDEF    370
    CMSPMSG     No            MATLAB      ?             SPELLFIX    370
    CMSPRT      No            MAXSTOR     No            SPELLLEX    370
    CMSPUN      No            MENUEXEC    See Xmenu     SPITBOL     ?
    CMSRAP      No            MODULE      XA            SPITLOAD    ?
    CMSREAD     No            NAMES       XA            SPLPREP     XA
    CMSTIO      XA            NAMESORT    XA            SSORT       See SyncSort
    COBOL (Debug) ?           NETCHECK    XA            SSORTF      See SyncSort
    COBOL (VS)  ?             NETCMD      XA            STATUS      XA
    CODETRAN    XA            NETNODE     XA            STK         XA
    COST        No            NETSTAT     370           STKCP       XA
    DELETE      XA            NEWFILES    ?             STKDATE     XA
    DI-3000     370           NEWS        370           STKDISK     XA
    DISKSIZE    XA            NICK        XA            STKFILE     XA
    DMS         ?             OPTIONS     370           STKID       XA
    DMSCVT      370           OUTPUT      XA            STKRDR      XA
    DOWNLOAD    ?             PACK        XA            STKTERM     XA
    DRONE       XA            PAINTSHO    370           STKTIME     XA
    DROP        XA            PANEL       See DMS       STKXRDR     XA
    ENVIRON     XA            Pascal (P4) ?             STORAGE     XA
    EUDCMSX     See DMS       Pascal (VS) XA            SUBMIT (CMS)  See BATCH
    EXPLAIN     No            Pascal (8000) ?           SUBMIT (MVS)  XA
    FFS         370           PASSWORD    XA            SUGGEST     XA
    FILESIZE    XA            PATH        370           SyncSort    370
    FINDJOB     XA            PCTRANS     ?             SYSID       XA
    FINDPRT     XA            PHASE       XA            TapeMap     XA
    FLIST       XA            PHONE       XA            TDISK       XA
    FORTRAN (VS)  XA          PHONEPRT    XA            TELL        XA
    FORTRAN Debug ?           PICSURE     370           TELNET      370
    FORTRAN G   ?             PING        370           TERMINFO    XA
    FORTRAN HX  ?             PLC         ?             TESTCOB     ?
    FPRINT      XA            PLOGOFF     XA            TKPLOT      ?
    FREE        XA            PLOT        ?             TPRINT      XA
    FSEND       ?             PLOTLW      370           UNPACK      XA
    FTP         370           PLOTTEK     370           UPLOAD      ?
    GATHER      See REPRINT   PRESERVE    XA            VERIFY      XA
    GDDM        370           Prolog (IBM)  370         VIEW        370
    GETFMODE    XA            PSEDIT      370           WAITRDR     XA
    GETVADDR    XA            PUBLIC      XA            WHOIS       XA
    GK-2000     370           PVM         370           XMENU       370
    GRAB        XA            QON         XA            YCALC       370
    Graphigs    370           QSF         ?
    GRIPE       XA            RANDOM      XA

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