Standalone mode uses temp DB files by default (RIPD-1129):

* If a [database_path] is configured, it will always be used, and tables
  will be upgraded on startup.

src/ripple/server/impl/ServerHandlerImp.cpp

@@ -770,7 +770,7 @@ parse_Ports (
         result.push_back(to_Port(parsed, log));
     }
 
-    if (config.RUN_STANDALONE)
+    if (config.standalone())
     {
         auto it = result.begin ();