provides background on concepts and terminology, at least as I understand.
Duplicati 2 (unlike Duplicati 1) uses standalone versions, plus deduplication.
If you purge a broken file, however many filesets/dlist it is in must reflect that.
The dlist is a full list of file paths, plus enough info to figure out the block use.
DB Fileset table is like dlist backup versions. FilesetEntry table names blocks.
All of this is SQL queries I think. The dlist is small compared to whole backup.
SQLite can use temporary files if memory runs out, but I think it’s more reads.
Similarly, it writes DB some as it goes, but that’s going to happen for anything.
The difference between dry-run and not in terms of remote writes is dlist files.
Some dblock file blocks will also turn into partially or completely now-useless.
This may trigger compact, which will delete or repackage, just like usual case.