每天在每两个小时运行一次但在一天的不同时间运行的脚本上，我们每天都会收到此错误。

ERROR at line 1:
ORA-04068: existing state of packages has been discarded
ORA-04061: existing state of package body "PACKAGE.NAME" has been
invalidated
ORA-06508: PL/SQL: could not find program unit being called:
"PACKAGE.NAME"
ORA-06512: at line 1

有人可以列出什么情况会导致此错误，以便我们进行调查吗？

谢谢。

更新：执行'ALTER SESSION CLOSE DATABASE LINK DBLINK'会使包的状态无效吗？