diff --git a/src/warden-server/doc/UPDATE b/src/warden-server/doc/UPDATE
index c9ce426ac2998573d0a82265d28b5426a277b9fd..e6dbefe32d615d027434bcc648a2eb49a954bea4 100644
--- a/src/warden-server/doc/UPDATE
+++ b/src/warden-server/doc/UPDATE
@@ -32,9 +32,14 @@ B. Update steps
 C. Post-update steps
 --------------------
 
-1) Update Warden server database
+1) Upgrade Warden server database
+
+	$ mysql -u <user> -h localhost -p <password> < {warden-server_path}/doc/warden21to22.patch
+
+
+ATTENTION: Running of the database update script may take a long time (in minutes - depending on the size of the database).
+During this process the database will be not available!
 
-	$ mysql -u <user> -h localhost -p <password> < {warden-server_path}/doc/warden20to21.patch
 
 
 2) Restart Apache server
diff --git a/src/warden-server/doc/warden21to22.patch b/src/warden-server/doc/warden21to22.patch
index 2a4ef4e21c0fe41cf7ff5748d54562a0c4065081..2278f44379438fa88f593ab8f8a7aa3ea6fa9dd0 100644
--- a/src/warden-server/doc/warden21to22.patch
+++ b/src/warden-server/doc/warden21to22.patch
@@ -11,3 +11,8 @@ WHERE `events.hostname` = `clients.hostname` AND `events.service` = `clients.ser
 ALTER TABLE `events`
 DROP COLUMN `hostname`,
 DROP COLUMN `service`;
+
+ALTER TABLE `events`
+ADD INDEX `idx_events_type_valid` (`type`,`valid`),
+ADD INDEX `idx_events_client_id` (`client_id`),
+ADD INDEX `idx_events_detected` (`detected`);