Conference turris::digital_unix

8887.0. "Problems reading IBM tapes" by VAXRIO::MIRIAM (Unix Group - CSC/Brazil) Wed Feb 19 1997 09:58

  Hi,

    A customer needs to read tapes generated by IBM systems in ANSI v3 format.
  He used to read this tapes on a DECsystem 5000/125 running ULTRIX v4.3 on a
  TSZ07 (FW rev. 0305) successfully.
    Now he upgraded his system to a Alphaserver 2100A with TSZ07 (FW rev 0309).
  He uses the same procedure he used to run in the Ultrix system but get invalid
  data read.
    The command he uses is:
      dd if=/dev/nrmt2h of=/tmp/file1.txt ibs=$IBS cbs=$CBS conv=ascii,sync

     where IBS is the block size in bytes and CBS is the record size got from
     the header file as described in 'man 4 ltf'.

   We can identify two different problems in the data read:
     1- The last block read has invalid data. It seems that dd is working with 
        'old data' because we find the contents of the previous records shifted.
        It seems that the last block is incomplete and dd is working with part
        of the previous buffer.
     2- Some characters are uncorrectly converted from EBCDIC. We identified 2
        characters with this problem: ']' is uncorrectly converted to '!' and
        '%' is also converted un correctly but I can't remember to what at the
        moment.

   Extra information:
     . wc always shows the correct nunber os lines but usually shows the wrong 
       number of characters
     . we moved the tape drive connected to the DECsystem to the Alpha but got
       the same problem
     . we read the same tape in the Ultrix system correctly


   Does anyone have an idea of the possible problem?
   Thanks in advance,

     Miriam