HP OpenVMS Systems

DCL Error Handling?

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The Question is:

 
I am trying to write a command file that reads tape that was mounted as
 foriegn.  A good tape would have 4 records where the first three are empty. If
 the system that generates these tapes (+25 year old HP computer) has a problem
 then it sometimes over wr
ites the tape and usually causes a 5th record to contain data some valid data.
 I have written a command file that reads the tape and store the data into
 files.  I am trying to test for the possibility of a 5 record and there are
 three possible conditions
that could occurs.  1st there is not data in the 5th record (blank - this is
 GOOD) 2nd there is a parity error (tapes recycled may have been at different
 density) and third there is valid data.  When the tape drive reads either a
 blank tape or parity erro
r I can capture the $STATUS into a LOG file which only indicated a read error.
 What I really would like to do is capture the specific  error message that
 indicated either "incomplete read" or "parity error".
 
Any help would be greatly appreciated.  I was a former assistant VMS system
 manager too many years ago to remember how to do this.  I have been reading
 the system manuals but have not found the key to solve this problem.
 
Thank you
 
 

The Answer is :

 
  Assuming the error code is not stored in the $STATUS symbol, then a
  program will likely be required.  You will also want to declare an
  ON ERROR handler, or use SET NOON.
 
  Note that DCL is not particularly suited for reading binary data.

  

     

     
answer written or last revised on ( 2-AUG-2000 )
     
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