C3P0连接问题请教

我在Hibernate中使用C3P0时，有时会出现一下错误：
Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:104)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:236)
at com.mchange.v2.c3p0.PoolBackedDataSource.getConnection(PoolBackedDataSource.java:94)
at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:35)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:417)
... 52 more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAcquire(BasicResourcePool.java:970)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:208)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:232)
... 55 more
请问这是咱们回事？
配置如下：
<hibernate-configuration>
<session-factory>
<property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:test</property>
<property name="connection.username">test</property>
<property name="connection.password">test</property>

<property name="connection.pool.size">2</property>
<property name="statement_cache.size">25</property>
<property name="jdbc.fetch_size">50</property>
<property name="jdbc.batch_size">30</property>
<property name="hibernate.show_sql">false</property>
<property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
<property name="hibernate.current_session_context_class">org.hibernate.context.ThreadLocalSessionContext</property>

<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.idle_test_period">3600</property>
<property name="hibernate.c3p0.max_size">10</property>
<property name="hibernate.c3p0.min_size">2</property>
<property name="hibernate.c3p0.max_statements">0</property>
<property name="hibernate.c3p0.timeout">3000</property>
.......
</session-factory>
</hibernate-configuration>