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tar tapes?

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The Question is:

OpenVMS Version: All
Re: tar and tape media interchange
Neither UN*X nor AIX supports ANSI labelled tapes natively. For tar to
be able to read tapes written on other systems, in general, the tape format
must conform to the appropriate RFCs. In specific, the following should be
successful for writing a tar tape that UN*X or AIX can read:
 1. Use VMStar to write a disk archive. The archive file should end up
    being Fixed-512. If not, use SET FILE/ATTRIB=(RFM=FIX,LRL=512). tar
    will handle the data on the tape when it reads it, even if it includes
    embedded LFs (that's UN*Xs "newline" character, after all).
 2. INIT the tape as usual, but be sure to omit the /MEDIA_FORMAT
    qualifier (or specify /MEDIA=NOCOMPACT).
 3. Use MOUNT/FOREIGN to mount the tape. The default blocksize is
    documented as 512 bytes, but you can help ensure this by specifying
    /BLOCK=512 on the MOUNT. (Actually, UN*X tar likes a 1024 byte record
    size, but you can experiment with this.)
 4. Use the COPY command to write the tar archive to the tape. Note that
    the archive must fit on a single tape when using this method.
That *SHOULD* produce a usable tar tape. If not, try writing the tape
directly from tar, and adjust the /BLOCKSIZE qualifier value as
needed (512 or 1024), but BE SURE TO MOUNT IT /FOREIGN to avoid
having a labelled tape!
Hope this helps.
David J. Dachtera
dba DJE Systems

The Answer is :

   The OpenVMS Wizard has found tar to be a common choice, but also a
   rather poor substitute for a reliable tape interchange scheme or a
   data archiving mechanism.  (Traditionally, tar simply "falls over"
   on an error.  Implementations of tar that the OpenVMS Wizard is
   familiar with also lack any form of error checking or redundency
   on the user data.)
   If the archive or the FTP transfer corrupts the file attributes of
   a file that is a BACKUP saveset, fhe Freeware command procedure
   FAQ -- will be of interest.  (Direct use of SET FILE with the correct
   file attributes will clearly also work, but this command procedure
   will read the BACKUP saveset's own block size as part of issuing the

answer written or last revised on ( 5-JAN-2001 )

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