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HP OpenVMS Systemsask the wizard |
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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 locations. 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 code. 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).
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