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Blocksize, estimating storage on a magtape?

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The Question is:

 
I am trying to find out how many bytes are in a standard VMS block.
 
I am copying files from a system to COMPAQ DLT IV tape media
with a density of 20Gb Compressed on a TZ88 tape drive.
 
Due to the size of the files I currently copy a single file to each
tape but think I should be able to copy more, but don't understand
the block sizes, I cannot allow files to span two tapes as the
person reading the files uses a UNIX program to read them and
the program cannot cope with this.
 
On the system the files block size is 19,828,620 which assuming
512 bytes per block (from another Query I read) is 10 Gb.  Have
I got this correct?
 
When I copy the file to tape the block size reads 314,740.  What
is the size of this file in bytes i.e. is it the same file compressed
into a 161 Mb file.  Also the other way around how many blocks
can I fit on a DLT IV tape, if I use 20Gb compress?
 
Thanks for your Help.
Regards,
Martin.

The Answer is :

 
  Please see the FAQ sections PROG14 and MISC13 as a start.
 

  
     
     answer written or last revised on ( 1-MAY-2000 )
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