> One caveat though: 7z files are like MS cab files. They are one
> continuous archive. ... This allows
> better compression but if you want to extract just a file, the entire
> archive must be decoded up to the location of the target file.
Applies for 7-zip in Solid mode (its strength compared e.g. to PKZip)
You can use 7zfm in Non-Solid mode as well:
in its 'Add to Archive' window, at 'Solid Block size' select 'Non-solid',
and you get quicker add/delete performance, to the costs of lower compression ratio.
Applies to cmdline mode (7z.exe) as well,
see 7zfm help window, search for '-m (Set compression Method) switch':
s=[off | on | {... snip ...} ]
Enables or disables solid mode. The default mode is s=on.
In solid mode, files are grouped together. Usually, compressing in solid mode improves the compression ratio.
To support both compression methods within ZTree, I've added an additional 7-zip entry in my Archiver.BB2 with option -ms=off ,
see Kim's comment block in the 7-Zip 9.20 for 7z [LFN,UNICODE,NAP] entry:
; Add '-ms=off' to the 'a' add lines to turn off creation of solid archives
; which allows individual files to be deleted inside the archive afterwards.
Hartmut