11.1开始，Data Pump会自动的重启一次job，不管是因为错误停止的，还是手工停止的。因此，如果我们希望手工的停止Data Pump job，需要stop两次。

Oracle® Database Utilities 11g Release 2 (11.2) -> What's New in Database Utilities?

* Automatic restart of workers on the same instance. Additionally, Data Pump now performs a one-time automatic restart of workers (on the same instance) that have stopped due to certain errors. For example, if someone manually stops a process, the worker is automatically restarted one time, on the same instance. If the process stops a second time, it must be manually restarted.