1 - Only ZIP and WDZ compression algorithms are available for backup purposes, zipCreate(..) doesn't accept RAR - you can only add(?) to or extract from existing RAR archives.

CAB: zipAddFile(..) stubbornly returned a 'no sufficient rights to add file' error though the referenced HFClassic-file is closed immediately before doing the zipAddFile(..) and a wait for completion of file-closing with Multitask()  as adviced to in WD Help. Imho, within a WinDev program CAB is unusable too.

2 - I couldn't find any difference in the resulting size of the compressed files after setting different levels of compression by MyArchive..compressionlevel = 1 -> 12 Suspiciously, in WinDev Help there’s no real advice about the recommended values for compressionlevel

3 - the results could be worse, but they're far off from being best in their class ..

My reference is 7-zip from http://www.7-zip.org/

Using 7-zip’s LZMA & LZMA2 algorithm + compression level 'Ultra' a dataset of 2,46 Gb (HF Classic files) resulted in a compressed file of about 88 Mb. Thus, 7-zip compressed the files to 3.58% of their original size.

Using WinDev ZIP the same dataset compresses to 259 Mb = 3 x bigger than .7z = 10.53% of orig. size

Using WinDev WDZ the same dataset compresses to 402 Mb = 4.5 x bigger than .7z = 16.34% of orig. size

Bottom line: If datasets aren’t too big and backup history is regularily taken care of ... at current hard disk sizes it probably doesn’t matter whether compression is down to 3% or to 10% only. However, if you expect your customers to have many backups and that they will not delete too old / unneeded backups then I’d recommend to have a look at the 7-zip command-line interface or to use the .dll of 7-zip!