From: dragon@NSCVAX.PRINCETON.EDU (Mighty Firebreather)
Newsgroups: comp.os.vms
Subject: RE: VMS/Un*x media exchange compatibilities
Date: 25 Jul 92 16:51:13 GMT
Distribution: world
Organization: The Internet


	Chris Marzec <MARZEC%GUNBRF.BITNET@VTVM2.CC.VT.EDU> writes:
>
>We are interested in methods of data exchange between VMS and other systems
>such as Un*x via magnetic tape media preferably DAT. At present we have been
>able to distribute to non-VMS sites by using the following protocol for mag
>tape and TK dirves:
>
>  1. rewrite VMS files from "variable length records / CR carriagecontrol"
>                         to "fixed-length 80-byte rec / CR carriagecontrol"
>  2. INITIALIZE tape device with some label
>  3. MOUNT/FOREIGN/RECORDSIZE=80/BLOCKSIZE=4800 device:
>                                          =2048 for TK50, TK70 (and DAT) tape

	This probably overwrites your label.  It certainly will result in 
no HDR1, HDR2, HDR3 labels being written and no trailer labels either!  If 
you MOUNT /FOREIGN you do not get an ANSI labeled tape!

>  4. COPY VMS-file device:
>
>In the past most all non-VMS sites were able to use this media. We assume that
>this protocol yields an industry standard ANSI-labeled tape. However, lately
>we attempted to distribute data via the above protocol except using a WangDAT
>Model 1300 DDS DAT tape drive. The system used is a VAXstation 3100 running
>V5.5. The customer was able to read/copy only the first file of the volume
>after which no more data was accessible. We are curious to get feedback from
>this protocol, specifically if it can be used for all non-VMS systems and if
>it is an efficient procedure (time and space).
>
>Questions:
>  1. is "VMS-ANSI-labeled" synonymous with "ANSI-labeled"

	Sort of.  There are various revisions or levels of the ANSI standard
and I believe that VMS uses level 3 while level 4 is the current version 
(or something like that).

>  2. the DAT drive spec for blocksize is 36, is this significant because we
>     are able to read the tape inhouse when made using the above protocol

	A blocksize of 36????? 36 byte blocks???  I don't believe it!  36K 
maybe?

>  3. does VMS file attributes affect the format of data when written to tape
>     ie. fixed-length vs. stream_LF (is one better than the other)

	For years, the one tape format that *any* system can read, has 
been 80 byte *unblocked* fixed length records with *no* labels!  With the 
advent of streaming cartridge drives, this may no longer be true.  It was 
never very efficient in terms of either speed or tape usage; it was just so
simple and standard that even the brain damaged could read it.

	These days anybody, with the possible exceptions of IBM and Unix 
systems should be able to read an ANSI labeled tape.

	To make an ANSI labeled tape:
$ ALLOCATE MUA0: TAPE
$ INITIALIZE TAPE label
$ MOUNT /BLOCKSIZE=xxxx /RECORDSIZE=yyy TAPE:
$ COPY MYFILE.DAT TAPE:
$
	If MYFILE.DAT has the fixed length record attribute, you will get 
fixed length records on tape.  If the records are 80 bytes long, you will
get 80 byte fixed length records.  If yyy is less than the actual record 
size you will get an error.  Blocksize defaults to 2048.  You might want to
use a larger value.

*************************************************************************
*                                                                       *
*                        Here, there be dragons!                        *
*                      dragon@nscvax.princeton.edu                      *
*                                                                       *
*                                                Richard B. Gilbert     *
*************************************************************************

Newsgroups: comp.os.vms