From: AITGW::"moeller%gwdgv1.dnet.gwdg.de@VTVM2.CC.VT.EDU" "GWDGV1::MOELLER" 22-NOV-1991 04:46:40.72 To: arisia::everhart CC: Subj: re^2: VMS BACKUP docs ... Received: by AITGW.DECnet (utk-mail11 v1.5) ; Fri, 22 Nov 91 04:46:03 EST Received: from vtvm2.cc.vt.edu by aitgw.ge.com (5.65/GE Gateway 1.4) id AA28486; Fri, 22 Nov 91 04:45:58 -0500 Message-Id: <9111220945.AA28486@aitgw.ge.com> Received: from DGOGWDG1.BITNET by VTVM2.CC.VT.EDU (IBM VM SMTP V2R1) with BSMTP id 8632; Fri, 22 Nov 91 04:44:25 EST Received: from dnet.gwdg.de by DGOGWDG1.BITNET (Mailer R2.07) with BSMTP id 2053; Fri, 22 Nov 91 10:04:55 MEZ Date: Fri, 22 Nov 1991 10:04:53 +0100 From: "GWDGV1::MOELLER" To: arisia::everhart Subject: re^2: VMS BACKUP docs ... Glenn, your mail headers are still wrong ... v------- quotes required here --------------------------v > From: Glenn Everhart 215 354 7610 Everhart%Arisia.dnet.ge.com > I have to admit that I find making a virtual disk out of a backup/physical tape rather weird, having not seen a single-tape backup for a long time ... > [...] though I will have to find > someone with the V3 utilities manual to find out how the CRC is done. > Backup has two polynomials it uses...autodin and crc16..and I suspect > I'll be able to isolate the correct one pretty fast. I know why I salvaged said manual ... let me quote (but please don't expect me to type in all of its appendix): BBH$L_CRC contains the CRC computed on the entire data block using the AUTODIN II CRC algorithm. The CRC field is set to 0 during the computation. If the flag bit BBH$V_NOCRC is set, this field contains 0. BBH$L_FLAGS contains the following flag bits for the block: BBH$V_NOCRC set if no CRC was computed for this block [no more bits mentioned - wjm] BBH$W_CHECKSUM contains a checksum of the block header computed by the CRC-16 algorithm. According to the accompanying figure, the offsets ought to be 36. for CRC, 44. for FLAGS, and 254. for CHECKSUM. > As for turning the SDI files to .H, I suspect unsdl (another of Joe > Meadows' goodies) seems likely to be helpful. I may not know the exact file types - on the "fiche" one only finds the SDL source, and lacking the SDL "compiler", UNSDL won't help. There are no binary BACKUP definitions distributed with VMS. > One day I'll need to see if I can build a client for > your remote tape that will run on unix, since I've got an 8mm on a vax > and an 8mm on a sun and would love to be able to do tape-tape > copies. Nice to hear that *someone* thinks about extending that beast. Maybe I mentioned in the past that I did port the tape server once - to our VM/CMS IBM DECnetted via INTERLINK (a rather unusual setup, I guess) - and found it very slow due to the network protocol (handshake) overhead. So far, I haven't learned anything about un*x tape handling. Wolfgang J. Moeller, GWDG, D-3400 Goettingen, F.R.Germany | Disclaimer ... PSI%(0262)45050352008::MOELLER Phone: +49 551 201516 | No claim intended! Internet: moeller@gwdgv1.dnet.gwdg.de | This space intentionally left blank.