[Info-vax] Backup TK50 tapes

[Steven Schweda]

   I haven't looked at a real STABACKIT.COM for a long time,
but I do have a DCL script to produce a MicroVAX Diagnostic
Monitor (VAX diagnostics) tape.  It mounts the destination
tape (typically a TK50) with /BLOCKSIZE = 512, and then uses
COPY /CONTIGUOUS to copy the boot-related files, SYSBOOT.EXE
and MDM.SYS to the tape.  Then it does a DISMOUNT /NOUNLOAD,
followed by a MOUNT /BLOCKSIZE = 8192, and then it copies all
the other files (mostly N%%%%.EXE) to the tape.  So, the
structure of this particular bootable tape is not perfectly
simple, but it's not especially complicated, either.

> The files on the tape are definitely save sets.  You don't
> want to "manage" them, you just want to copy them.

   Which "the files" on which "the tape"?

   According to my dim recollection (subject to change
without notice) ...

   An official DEC two-tape TK50 VMS V5.x installation kit
has Standalone BACKUP at the beginning of the second tape,
followed by the DECwindows kit files (BACKUP save sets).  The
first tape has the primary VMS kit files (BACKUP save sets),
but no Standalone BACKUP.  So, one boots Standalone BACKUP
from the second tape, and then uses it to install VMS from
the first tape (and then the second tape, when so directed,
if installing DECwindows).

   The official VMS (VAX) installation instructions should
agree with this, if it's accurate.

   When I made my own VMS installation tapes, I found that I
could fit everything onto one tape, but the DEC-supplied kits
used two tapes.  I used STABACKIT.COM to install Standalone
BACKUP on a tape, and then I used MOUNT and COPY to copy the
kit files to the tape.  I don't remember specifying any
particular block size, so I'd guess that I was using the
default, 2048.  One would need to look at STABACKIT.COM to
see how it does things to see if it uses any special MOUNT
options.

   One could unpack a save set, and then use BACKUP to
recreate it as it writes to tape, and that might have some
advantages in error recovery, but, if one has the save sets,
then it's pretty easy to use COPY to write then to a tape. 
On a TK50, I'd avoid /READ_CHECK and /WRITE_CHECK.  It's much
faster to use DIFFERENCES to compare the files on tape with
the originals.