I have 5 tables:
fact table: readings(id,mu_id,reading)
dim table: mus(mu_id, name, parent_id) - parent-child relationship
closure table : mus_closure(parent_id,mu_id,distance)
agg table: agg_c_10_readings(mu_id, reading, fact_count)
agg_readings_mu_dim$closure(parent_id, reading, fact_count)

Mondrian cube:
<?xml version="1.0"?>
<Schema name="Readings">
<!--
== $Id: //open/mondrian-release/3.2/demo/FoodMart.xml#2 $
== This software is subject to the terms of the Eclipse Public License v1.0
== Agreement, available at the following URL:
== http://www.eclipse.org/legal/epl-v10.html.
== Copyright (C) 2000-2002 Kana Software, Inc.
== Copyright (C) 2002-2009 Julian Hyde and others
== All Rights Reserved.
== You must accept the terms of that agreement to use this software.
-->

<!-- Shared dimensions -->

<!-- Readings -->
<Cube name="Readings" defaultMeasure="ReadingMeas">
<Table name="readings"/>
<Dimension name="MU_DIM" foreignKey="mu_id">
<Hierarchy hasAll="true" allMemberName="All MUS" primaryKey="mu_id">
<Table name="mus" />
<Level name="MU" uniqueMembers="true" type="Numeric" column="mu_id" nameColumn="name" parentColumn="parent_id" nullParentValue="null">
<Closure parentColumn="parent_id" childColumn="mu_id">
<Table name="mus_closure"/>
</Closure>
</Level>
</Hierarchy>
</Dimension>
<Measure name="ReadingMeas" column="reading" aggregator="sum" formatString="Standard"/>
</Cube>
</Schema>

When mondrian sums over "All Members" level it correctly uses 'agg_c_10_readings' table but doesn't use agg table when i drill down below "All Members". If i remove the closure tag from the above cube definition, it starts picking up the agg table 'agg_c_10_readings' correctly.

I also created an agg table, agg_readings_mu_dim$closure (aslo tried agg_readings_mus$closure), as suggested in the documentation, but it's not used when i drill to a level below 'All Members'. Anyone, please suggest, where am i wrong.

TABLES:
CREATE TABLE `agg_c_10_readings` (
`mu_id` int(11) NOT NULL,
`reading` int(11) NOT NULL,
`fact_count` int(11) NOT NULL
) ENGINE=InnoDB;

CREATE TABLE `readings` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`reading` decimal(30,6) NOT NULL,
`mu_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=85;

CREATE TABLE `mus` (
`mu_id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
`parent_id` int(11) DEFAULT NULL,
PRIMARY KEY (`mu_id`)
) ENGINE=InnoDB AUTO_INCREMENT=7;

CREATE TABLE `mus_closure` (
`parent_id` int(11) NOT NULL,
`mu_id` int(11) NOT NULL,
`distance` int(11) NOT NULL
) ENGINE=InnoDB;