sdm7g@dale.acc.Virginia.EDU (Steve D. Majewski) (09/27/90)
As far as I have been able to decipher, VAX/VMS RMS leaves ONE byte
in the file header that can be user defined. ( I believe it is
FH1$B_USERCHAR, but it's been a while since I poked around. )
1) Is this still "reserved for users" , or has DEC taken it back
to reserve for something else?
2) Has anyone out there actually tried to use it for anything ?
[ What I had in mind, once, long ago, was modifying the I/O to ]
[ do auto-magic file compression/decompression: If the right bit ]
[ in FH1$B_USERCHAR is set, then the first item in the file is ]
[ the decompression map :: decompress and unblock the records ]
[ on reads. This obviously would entail re-vectoring SYS$OPEN, ]
[ SYS$READ, SYS$GET, etc. Other info that could tag along ]
[ could be audit trails, file comments, etc., the idea being that ]
[ the extra data would be invisible to "normal" reads, and the ]
[ files still compatable with their applications. ]
[ The necessity of doing this on VMS has passes, as we are moving ]
[ more applications over to UNIX, but I am still curious about ]
[ whether my original notion was practical. And I am interested ]
[ in comparing the difficulty of the same project in VMS vs UNIX. ]
3) Has DEC ever published anything on RMS/ODS/File&I/O systems as
exhaustive as the black book on VMS internals? Or anything ?
If you reply via E-mail, I will summarize and post.
- Steve Majewski sdm7g@virginia.edu
========================================================================
Steven D. Majewski University of Virginia Physiology Dept.
sdm7g@Virginia.EDU Box 449 Health Sciences Center
(804)-982-0831 Charlottesville, VA 22908munroe@dmc.com (10/01/90)
In article <1990Sep26.182837.618@murdoch.acc.Virginia.EDU>, sdm7g@dale.acc.Virginia.EDU (Steve D. Majewski) writes: > > 3) Has DEC ever published anything on RMS/ODS/File&I/O systems as > exhaustive as the black book on VMS internals? Or anything ? > The newest version of the VMS IDSM book apparently has a substantial section on the ODS2 XQP/ACP. Since I haven't seen a copy yet, I can't speak from personal knowledge, but I have it from a "reliable source". -- Dick Munroe Internet: munroe@dmc.com Doyle Munroe Consultants, Inc. UUCP: ...uunet!thehulk!munroe 267 Cox St. Office: (508) 568-1618 Hudson, Ma. FAX: (508) 562-1133
terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr) (10/02/90)
In article <1347@dmc.com>, munroe@dmc.com writes: > The newest version of the VMS IDSM book apparently has a substantial > section on the ODS2 XQP/ACP. Since I haven't seen a copy yet, I can't > speak from personal knowledge, but I have it from a "reliable source". Maybe you mean "VMS File System Internals", order # EY-F575E-DP, a sep- erate book? It discusses ODS-2 and the XQP/ACP, but doesn't have a lot to say about RMS... Terry Kennedy Operations Manager, Academic Computing terry@spcvxa.bitnet St. Peter's College, US terry@spcvxa.spc.edu (201) 915-9381