Update README.md

README.md

@@ -31,7 +31,7 @@ The supervision and failover relies on the contributions of
 
 1. ca-supervisor is running and does not crash in any of the procedures involved
 
-2. the dedicated caserver [plugin](https://gitlab.elettra.eu/puma/server/ca3-db-plugin) is loaded.
+2. A database (PostgreSQL) with the dedicated caserver [plugin](https://gitlab.elettra.eu/puma/server/ca3-db-plugin).
 
 3. one *ca-proxy* talks with only one *caserver async* (and one only *caserver sync*, but the latter is not relevant in the recovery context)