based on your description I would say that the two scans have used different DATs thus they had to scan everything (which was not specifically excluded). My understanding about scan cache is that it is used to omit files from scanning that have not been modified as long as it is the same DAT on the computer to be used for any OAS or ODS (depending on a checkbox) scanning.
Also please check if "Allow on-demand scan to utilize scan cache" option is checked in the Tools - General Options - Global Scan settings section of VSE console.
I confirm, the option is activate. Just for understand, what is OAS or ODS ??
And if I understand your answer, the new scan of my latop use cache if the DAT is the same between the first and the second scan ?But in my case, we update every day the DAT to have the latest virus definition. In this cas, whith an update of my DAT every day and a scheduled scan planned every monday, the scan will nerver use the cache because between 2 scan, we have updated the DAT file ?
OAS: On-Access Scan, ODS: On-Demand Scan
Yes the scheduled scan (ODS) will never use the cache, because either 1) the DAT is always newer when it runs than the one it used last time to scan the files, so it must scan again, or 2) because the cache only contains data on files that were already scanned with that version of DAT - and I suppose not every file gets scanned by OAS every day - so the ODS must scan every file because their current scan data is not in the cache.