Check mtaserver.conf and ensure is:
<dbfile>logs/db.log</dbfile>
start runcode and enter these commands via the client console (F8):
run db = dbConnect( "sqlite", "test.db" )
run dbQuery(db, 'SELECT a')
Then check for the file mods/deathmatch/logs/db.log
If it does not exist, ensure the permissions of mods/deathmatch/logs allows for file creation by the MTA server