sometime the connection from application to database will drop and i get SQLState: 08006 error Code: 17002. Below is my configuration for database pooling

 <prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
                <prop key="hibernate.use_sql_comments">true</prop>
                <prop key="hibernate.cglib.use_reflection_optimizer">true</prop>  <!-- true ==start up slower, but performacen on runtime good-->
               <prop key="hibernate.hbm2ddl.auto">update</prop> 
                <prop key="hibernate.c3p0.min_size">5</prop>
                <prop key="hibernate.c3p0.max_size">20</prop>
                <prop key="hibernate.c3p0.timeout">1800</prop>
                <prop key="hibernate.c3p0.max_statements">100</prop>   <!-- c3p0's PreparedStatement cache. Zero means statement caching is turned off. -->

Can anyone advise, should i use validationQuery, onBorrow.. and why need to use it? what other properties should i use to enhance stability of the connection from my application to oracle10g?