求助jdbc以system 连接 oracle 10g 权限不足

1.在sql*plus下已由sys 账号 将sysdba 权限赋值给 system; 
2.在sql*plus 和em管理器下都可以创建和修改数据库 
3.在spring 配置dataSource 
代码如下： 
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"> 
    <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"> </property> 
    <property name="url" value="jdbc:oracle:thin:@202.114.23.65:1521:EMSDB"> </property> 
    <property name="username" value="system"> </property> 
    <property name="password" value="seven"> </property> 
    <property name="maxActive" value="100"> </property> 
    <property name="maxIdle" value="30"> </property> 
    <property name="maxWait" value="50"> </property> 
</bean> 
测试代码如下： 
BasicDataSource ds  = (BasicDataSource)ctx.getBean("dataSource"); 
Connection conn = ds.getConnection(); 
Statement stmt = conn.createStatement(); 
    stmt.execute("delete from SYS.MES_MAINTENANCE_PLAN"); 错误信息： 
exception in thread "main" java.sql.SQLException: ORA-01031: 权限不足 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111) 
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:330) 
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:287) 
at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:742) 
at oracle.jdbc.driver.T4CStatement.doOall8(T4CStatement.java:206) 
at oracle.jdbc.driver.T4CStatement.executeForRows(T4CStatement.java:945) 
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1159) 
at oracle.jdbc.driver.OracleStatement.executeInternal(OracleStatement.java:1678) 
at oracle.jdbc.driver.OracleStatement.execute(OracleStatement.java:1644) 
at org.apache.commons.dbcp.DelegatingStatement.execute(DelegatingStatement.java:264) 
at test.MaintenancePlanDaoImplTest.main(MaintenancePlanDaoImplTest.java:47) 
大家帮帮忙呀! 
谢谢各位啦