Mksysb tape data recovery

[emze]

I am trying to recover data from a mksysb tape with an overwritten header. It was backed up from a Power 5 server running AIX 5.3
All data sectors beyond the header are untouched and fine. The header was overwritten by a faulty smit command to "check
the readability of the tape" that instead overwrote the header with the current date and showing a silly 0-byte backup. The
actual data is fine because I killed the rogue smit command as soon as I saw it was writing to tape in a few seconds, so it
didn't have time to damage the data sectors.
Two of the major data recovery shops talk big to get you to send the tape and then they sheepishly say they can't recover the data.
It occurred to me the problem must be the data is compressed by AIX when creating the mksysb tape using what I suppose is
a proprietary AIX compression, and that's why they couldn't do it.
Does anybody know if there's IBM software out there than can read the compressed data? I would like to avoid further
useless back and forth with this tape. Thanks!

 

[cspilman]

If my memory serves me correctly, mksysb structure is in 4 parts. the 4th, or last part, is you backup data and is in backup/restore format.

You may be able to try the following to see if it's still readable:

restore -s4 -Tvf <file> or <device>

example if it's your tape drive:

restore -s4 -Tvf /dev/rmt0

if it's readable, then you can replace the the T with an X and should restore your data just fine.