Every few months I delete my home-assistant_v2.db file, but the last time I did this I saw two more files that I am not familiar with:
-rw-r--r-- 1 root root 866.4M Dec 22 11:35 home-assistant_v2.db
-rw-r--r-- 1 root root 32.0K Dec 22 11:35 home-assistant_v2.db-shm
-rw-r--r-- 1 root root 5.0M Dec 22 11:36 home-assistant_v2.db-wal
What are the db-shm and db-wal files?
they are temp files for sqlite (the database), delete them too.
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 
will never happens again, sorry if i “touched” your feelings
