Cause
There is a lock on a library object when doing the export.
Error: ORA 4021
Text: time-out occurred while waiting to lock object
-------------------------------------------------------------------------------
Cause: While trying to lock a library object, a time-out occurred.
Action: Retry the operation later.
Bug 3386590 4021: TIMEOUT OCCURRED WHILE WAITING TO LOCK OBJECT
Fixed In Ver: 10.2.
ORA-04021说明正在遇到LIBARY CACHE PIN ，LIBARY CACHE LOCK
等会再去做吧
