错误现象：

ORA-02020: too many database links in use

Cause: The current session has exceeded the INIT.ORA open_links maximum.

Action: Increase the open_links limit, or free up some open links by committing or rolling back the transaction and canceling open cursors that reference remote databases.

再查看参数：

SQL> show parameter open_links;

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

open_links integer 10

open_links_per_instance integer 4

Oracle默认是4:

SQL> alter system set open_links=10 scope=spfile;

重启下数据库就好了!