On Mon, Jan 29, 2018 at 2:41 PM, Bill Ashton <[email protected]> wrote:

> Hey you UNIX/BPXBATCH experts!
>
> I have a friend at another company who just called me with a question I
> could not answer, but I hope that someone here can.
>
> He ran into an error using BPXBATCH for a PAX command, but could not find
> any documentation after searching on Google for nearly an hour. The error
> message looks like this - *pax: checksum error on tape (got #####, expected
> 0)*
>

​I think this means that the PAX archive is corrupt. Did you ensure that
it's trail amongst all systems was a BINARY one?​

​I am not an expert on this, but I think that there is a "hash value"
(checksum) associated with the PAX archive. The PAX command which creates
the archive adds in some "extra" so that the overall checksum is zero. So,
when the PAX command does a checksum on the PAX archive, if the calculated
value is not zero, the command knows that the data was been improperly
modified (corrupted).

IOW, the #### value does not have any real meaning, it was the result of
the calculation. Kind of like doing: f(x,y) in such a way that it is
guaranteed to have a result of 0. If f(x,y) != 0, then you know that either
x or y or the equation is incorrect. ​

ref: http://pubs.opengroup.org/onlinepubs/009695299/utilities/pax.html

====

The *chksum* field shall be the ISO/IEC 646:1991 standard IRV
representation of the octal value of the simple sum of all octets in the
header logical record. Each octet in the header shall be treated as an
unsigned value. These values shall be added to an unsigned integer,
initialized to zero, the precision of which is not less than 17 bits. When
calculating the checksum, the *chksum* field is treated as if it were all
spaces.

====



>
> and the ##### is some hex value, like eb0a or 1015b. He got this even
> though he wasn't even using tape - must be a standard message.
>
> Does anyone here know where to find these checksum errors so we can help
> him out?
>
> --
> Thank you and best regards,
> *Billy Ashton*
>


-- 
I have a theory that it's impossible to prove anything, but I can't prove
it.

Maranatha! <><
John McKown

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