add note about procedures

Author: nadja-muller

modules/ROOT/pages/queries/statement-types.adoc

@@ -9,4 +9,10 @@ Cypher knows the following different statement types:
 * Read query, which do not modify the data on your database, such as `MATCH (n) RETURN n`
 * Write query, which modify the data on your database, such as `CREATE (n) RETURN n`
 
-Queries executed in the same transaction must either be of the same type, or a combination of schema modifications and read commands.
+Queries executed in the same transaction must either be of the same type, or a combination of schema modifications and read commands.
+
+[NOTE]
+====
+Calling procedures on the system database does not count as an administration command.
+They are categorized either as a read or write query depending on the defined mode.
+====