hibernate 二级缓存中怎样清空set

Question

<set cascade="all" inverse="true" lazy="false" order-by="ORDERBY"  name="children"> 
      <cache usage="read-write" />
      <key column="PARENT_ID" />
      <one-to-many   class="TCompany" />
    </set>      
    <many-to-one cascade="save-update" update="true" insert="true" class="TCompany" column="PARENT_ID" name="parent"  lazy="false" />