The Oracle user SYS owns all base tables and user-accessible views of the data
dictionary. No Oracle user should ever alter (UPDATE, DELETE, or INSERT) any rows
or schema objects contained in the SYS schema, because such activity can compromise
data integrity. The security administrator must keep strict control of this central
account.

SYS用户：数据字典的拥有者
1. 没有Oracle用户能更改sys方案下的对象 ，这样的操作将危及数据完整性