IVIS-46: - Updated Database layer chapter.

docs/basic_concepts/database_layer.rst

@@ -1,2 +1,23 @@
 Database Layer
 ==============
+
+    * `Database information`_
+    * `Integrity`_
+
+Database information
+--------------------
+
+Currently iVIS database represented by `MySQL <http://www.mysql.com/>`_.
+
+You can change it in properties (*JdbcDriver*, *JdbcUrl*, *Hibernate.dialect*).
+
+.. note::
+    Using something other database instead MySQL not tested.
+
+Integrity
+---------
+
+Reporting about changing of information storing in DB something other way (e.g. manually run sql script) instead
+Hibernate is missing.
+
+If database has not mapped on entity columns, they are ignored by Hibernate.