Incremental tape re-use

[Doug Evans <DE%phoenix.sch.symbolics.com@RELAY.CS.NET>]

    Date: Mon, 24 Jul 89 15:23 CDT
    From: dmitchell@backus.trc.amoco.com (Donald H. Mitchell)

    WARNING: NEW USER QUESTION--

    I have a low volume of file changes on my lonely Symbolics and wanted to
    minimize tape storage; therefore, I tried using the "leave" value for
    the "tape when done" field on the incremental backup thinking that I
    should be able to append the next backup at the end of the previous one.
    Well, two or three cold boots later, I tried doing an incremental backup
    and got the warning that doing so would be hazardous to my tape's life.
    Did I miss something or should I infer that "leave" is very temporary?
    Is there anyway to do more than one backup to the same tape?

[Added Bug-Tape and Bug-Doc]

This looks like another small but important piece of information that
fell thru the cracks.  

The cart tape system on Lisp Machines does not support append operations.
This means one dump per tape if the dump is smaller than 45MB (20MB on
3600s).  Also, there used to be a bug in the LMFS programs that kept a
logical end-of-tape mark from being written at the end of the dump unless
you selected "rewind" in the dump menu.

[Bug-Tape: Is either of these things still true? ... or have they been
patched in some way?]

[Bug-Doc:  I can't find any references to either of these items in the
on-line doc.  I thought that the caution about no appends on cart tapes
was documented.]

If you have a reel-to-reel tape drive, what you describe should work.