I have an object mapped as following:

<hibernate-mapping>
<class name="idiada.zeus.domain.File" table="_FILE" schema="dbo" catalog="APP_ZEUS">
<id name="id" type="int">
<column name="ID" />
<generator class="identity" />
</id>
.....
<many-to-one name="product" class="idiada.zeus.domain.ZProduct" fetch="join" lazy="false" >
<column name="PRODUCT_ID" length="51" />
</many-to-one>
.....
</hibernate-mapping>

For field "product", which is a normal entity, when setting fetch mode to "select" works normally returning the object.

Changing the fetch mode to "join" causes an abnormal functionallity when there are several connections which causes the CPU increase the workload over 300% and creates lots of "jtdsXXXXX.tmp" files into Tomcat temp folder.