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Virtual Addressing? 32- or 64-bit Kernel?

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The Question is:

1. Is OpenVMS a 64-bit OS or 32-bit one?
2. What instuction (command) can help me to get the kernel information, such as
 kernel bits?

The Answer is :

  It would appear you are attempting to map your understanding of another
  operating system environment onto that of OpenVMS.  Accordingly, the
  OpenVMS Wizard would strongly recommend reading through at least some
  of the available OpenVMS documentation -- the terminology and general
  operations associated with common computing concepts can and do differ
  among various different operating systems.
  OpenVMS VAX provides 32-bit virtual addressing, while OpenVMS Alpha
  provides both 32-bit and 64-bit virtual addressing capabilities.
  OpenVMS I64 provides both 32-bit and 64-bit virtual addressing, as
  well.   Physical memory addressing capabilities can and do vary by
  the particular VAX, Alpha, or I64 system implementation.
  The OpenVMS Wizard will here assume you are familiar with the features
  and benefits of virtual addressing, and with the difference between
  virtual and physical addressing.  (If not, most operating system texts
  will describe these and related concepts in some detail.)
  OpenVMS does not particularly have a concept of kernel information as
  implied in your second question, and the OpenVMS Wizard will assume you
  seek the equivalent of the Linux uname -a command.  The OpenVMS kernel
  itself is normally identified by the displayed OpenVMS version number
  -- via the first line of the SHOW SYSTEM command, and via various DCL
  lexical functions, among other ways:
    $ type = f$getsyi("arch_type")
    $ name = f$getsyi("arch_name")
    $ write sys$output -
      "Executing on the ''name' architecture; numeric type: ''type'"
    $ vers = f$getsyi("VERSION")
    $ write sys$output -
      "Running OpenVMS ''name' version is ''vers'"
  There are internal version numbers on various kernel structures, though
  this level of detail is generally only of interest to the LINKER and to
  the image activator.  These version numbers are associated with specific
  parts of the kernel, and the LINKER and the image activator use these
  to determine whether kernel-mode code should be allowed to activate.
  For the user-level analog of this kernel-mode version control mechanism,
  please see the GSMATCH information available in the OpenVMS Shareable
  Image Cookbook and please see the OpenVMS LINKER manual.
  The system service equivalent of the f$getsyi -- sys$getsyi[w] -- is
  available for use within application programs.
  OpenVMS targets upward-compatibility of user-mode code and APIs, and
  also works to maintain compatibility of kernel-mode code as well.
  (Please see topic (7555) for related information, among other topics.)
  User-mode code -- code which is lacking latent bugs, and using supported
  and documented APIs -- is normally expected to continue operating after
  an OpenVMS upgrade.  Inner-mode (privileged-mode) code is generally
  also expected to continue to operate after most OpenVMS upgrades, but
  checks are in place to detect and report the need to rework kernel-mode
  code due to changes in the OpenVMS kernel.  More details in (7555).
  For related information, please see the "OpenVMS Alpha Terminology"
  section in the OpenVMS FAQ -- this in addition to the OpenVMS manuals.
  For user operations, see the User's Guide.  For user-mode programming
  and an introduction to programming in general, see the Programming
  Concepts Manual.  For kernel-mode code, see the OpenVMS device driver
  documentation and the Internals and Data Structures Manuals -- the
  inner-mode programming books are available from Digital Press, and
  are not part of the OpenVMS documentation set.
  Related topics include (173), (866), (1052), (1171), (1904), (2738),
  (2932), (4336), (6049), (7152), (7555) and likely other topics.
  One-line questions are exceedingly difficult to answer.  The above
  answer text is intended to answer some of the more common variants
  of the questions posed, with supporting details and elaboration.
  There are other interpretations, however.  Please consider providing
  more than one or two lines when asking questions, as is requested in
  the introductory materials in the ATW area -- this background can
  help the OpenVMS Wizard answer the question actually intended, and
  tailor the answer to your particular requirements.

answer written or last revised on ( 22-JUL-2003 )

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