They are temporary files created and “flushed” when ever …
db-shm is a shared memory file for temporary data only, i.e during requests etc
db-wal … read all about it https://www.sqlite.org/wal.html
i-e if/when you through developer-tools/services choose service “purge all, repack” , then ( in another window ) monitors /config folder ( i.e over samba-share ) , u’ll see it in action, wal is" pumping up" the purged _v2.db file
EDIT: ohh pedro got ahead of me