#558 7z not being recognized as one

[Charles S Galloway]

Hi. I have a 7z file that is not being recognized as a 7z. To that end, the file is:

7/25/2021 18:44 79,673,565,205 Z_PICS.7z

Is there a way I can send you the file so that you can see what is wrong please?

[Igor Pavlov]

What error message do you have?
Show first 48 bytes and last 128 bytes in hex.

[Charles S Galloway]

[C:\ZZ_Done\7Z_0001]"c:\Program Files\7-Zip\7z.exe" t Z_PICS.7z

7-Zip 23.01 (x64) : Copyright (c) 1999-2023 Igor Pavlov : 2023-06-20

Scanning the drive for archives:
1 file, 79673565205 bytes (75 GiB)

Testing archive: Z_PICS.7z
ERROR: Z_PICS.7z
Z_PICS.7z
Open ERROR: Cannot open the file as [7z] archive


ERRORS:
Is not archive

Can't open as archive: 1
Files: 0
Size:       0
Compressed: 0

[C:\ZZ_Done\7Z_0001]

[Charles S Galloway]

will post "Show first 48 bytes and last 128 bytes in hex." later today/ not sure how to do it yet

[Charles S Galloway]

the first page of the 7z in hex - will post the bottom lateer

[Igor Pavlov]

https://7-zip.org/recover.html
Read section "There is no correct End Header at the end of archive".

archive creation operation probably was interrupted by some reason. And in that case probably there are no Metadata Block and End Header at the end of archive.

If you used multi-volume option to create that archive, it can be another problem.

Think about all conditions and settings that were used to create that archive, and think why archive creation operation was interrupted.

You can recover some raw data without file names.
But recovering can be difficult, because archive is big.
And you need new program that will parse all lzma2 blocks in raw stream. Now I have no such program.

[Charles S Galloway]

Some special new software is required that will parse all lzma2 chunks.

Is that something you might consider creating?

Is there some where can upload the file to? for you to test with?

[Igor Pavlov]

I have no plans to develop that recovering code.
And it will not recover all your data.
It can recover some of your data.
Also recovering can be difficult.
And you will have no real filenames.
you can get such result:

file1.extension
file2.extension
file3.extension
...
file99999.extension

if your files are important, keep the archive for future, when recovering software will be available.
Or hire someone to try to recover it now.
some recovring instructions are here:
https://7-zip.org/recover.html
but it will recover only part of your archive.
you need new lzma2 parser also.