diff --git a/README.rst b/README.rst
index 9039cd0..02d0279 100644
--- a/README.rst
+++ b/README.rst
@@ -195,6 +195,18 @@
       controller:
         update_cells: true
 
+Increase number of chunks for online db migrations:
+
+.. note:: This only should be done in offline as large number of
+   rows locked by this process may cause service outage, which
+   may not be expected.
+
+.. code-block:: yaml
+
+    nova:
+      controller:
+        db_migrations:
+          max_count: 5000000
 
 Configuring TLS communications
 ------------------------------