fixing broken .Z files?

Jules Richardson wrote: ... ... There is a fundamental problem why it is not tractable in general. The whole point of a compressor is to get rid of the redundancy as much as possible (some of course are better than others with a given input file). It is exactly that redundancy that makes automated recovery possible. Disk recovery relies on the fact that everything is cross linked with everything else so you can fix up the broken sector chains etc. If you happen to have very specific knowledge about the failure mode and the lost/corrupted/inserted data is just a small amount it might be possible to have an automated aid to assist in recovering the data, but mostly everything downstream from the failure is going to be lost. Even though G4 compression is 2x as effective as G3 compression (on bilevel images), fax machines still use G3 because any error propagates to the end of the scan line whereas the same error in a G4 file can trash the image all the way to the end of the page. If the entire tape is compressed as a stream, then things are very bad indeed. If the tape image compresses each file individually, then it should be possible to skip for a while and find a good new starting point.