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Details of ODS-2 and ODS-5 disk structures?

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The Question is:

I want a complete technical specification
which completely describes the ODS2 and
ODS5 file systems.
I understand there was no ODS5 file system
specification as of May 1999, but perhaps
there is now?
Is there an ODS2 file system specification?
A detailed description of an example ODS2
formatted floppy disk or ODS2 formatted hard
disk layout where the file system structures
are described relative to their disk block
I know that a partial ODS2 description exists
in the book VMS FILE SYSTEM INTERNALS but the
ODS2 description is incomplete, that is, it
does not provide enough information to describe
the ODS2 file system to the point that I could
write an ODS2 formatter or ODS2 file system
handler for use on a Linux system, for example.
I also am aware that some ODS5 information is
included in the new VMS documentation but the
information is limited and incomplete.
I know I could spend a couple of thousand
dollars and buy an OPENVMS source code CD but
this is too  costly.  I am hoping there is
other printed documentation which comprises
most or all of a complete technical description
of at least ODS2 and hopefully ODS5 as well.
I have a some ODS2 reader C language code
floating around the Internet that has also
found its way  onto the V4 OpenVMS Freeware CD,
but again, this source code does not completely
document the ODS2 file system.  In fact this
source code provides little documentation at
all, but I am referring to the implied
documentation derived from studying the C source
All of the foregoing sources of ODS2/ODS5
information are very useful, but it would still
be very, very helpful if I could obtain a
better and more complete technical description
of the ODS2 file system (ODS5, too!).
Does any such documentation exist internally
at Compaq, presumably within the OpenVMS
operating system development group?  If so,
how can I get a copy?  Can you refer me to
someone within the OpenVMS operating system
development group to pursue this further?
I have tried going through Compaq/Digital
hardware and software support and yes, I do
have lots of VAX and Alpha VMS systems under
both h/w and s/w support contracts.  The
attempts have always resulted in being told
I would be helped, that someone would call
me back, and then silence ...
So I am trying ASK THE WIZARD.
Thanks for any help you can provide.
I hope you can send me a direct email reply
if this is possible.
Steven Ward     sward@cfa.harvard.edu

The Answer is :

  The only currently-available resources are the "VMS File Systems Internals"
  book by Kirby McCoy, available from Digital Press (http://www.bh.com/),
  the contents of the OpenVMS definition libraries, and the OpenVMS source
  listings CD-ROM sets:
    QB-MT1AB-E8      OpenVMS Alpha Source Listings CD-ROM
    QT-MT1AB-Q8      OpenVMS Alpha Source Listings CD-ROM Updates
    QB-001AB-E8      OpenVMS VAX Source Listings CD-ROM
    QT-001AB-Q8      OpenVMS VAX Source Listings CD-ROM Updates
  The ODS-2 and ODS-5 on-disk formats differ in the addition of the $FI5DEF
  to the existing $FI2DEF structure found on existing ODS-2 disks.  Further,
  OpenVMS V7.2 and later do permit a larger BITMAP.SYS file, on both ODS-2
  and ODS-5 disks, which permits smaller disk cluster factors to be used.
  Using the combination of the information and knowlege gained from the
  "VMS File Systems Internals" book, the definition files in the OpenVMS
  system libraries, the OpenVMS source listings, and -- when necessary
  -- some basic trial and error on an OpenVMS system, determining the
  specific details of the ODS-2 and ODS-5 implementation should not be
  particularly difficult.  (You could alternative access a disk via
  the OpenVMS XQP, and then MOUNT/FOREIGN the same disk and access it
  via your test tool(s).)
  There are various ODS-2 readers available, including the one you have
  mentioned that is located on the OpenVMS Freeware V4 CD-ROM set.
  Your request for a specific block-level description of an ODS-2 or ODS-5
  disk should be covered by the description of volume initialization and
  the associated processing that is included in the "VMS File Systems
  Internals" book.  Neither ODS-2 nor ODS-5 generally tie the on-disk
  structures to specific disk blocks, and are also now largely free of
  any geometry-based structure restrictions.
  The processing of the ODS-2 and ODS-5 format is just the beginning of
  the process, as OpenVMS Record Management Services (RMS) adds record
  capabilities and structures onto the ODS-2 and ODS-5 disk structures
  provided by the OpenVMS XQP.
  If you have found any omissions or specific errors in "VMS File Systems
  Internals", the OpenVMS Wizard would be interested in hearing about
  them -- yes, ODS-5 is not currently covered, see $FI5DEF in the library
  SYS$LIBRARY:LIB.MLB.  Most (all?) other similar ODS-related data structure
  definitions are also included in LIB.MLB.
  Also see topic (2082).

answer written or last revised on ( 23-JUL-2001 )

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