分别创建2个db link，1个private db link，1个public  link

SQL> create database link tps connect to scott identified by tiger using 'orcl';

Database link created.

SQL> create public  database link pps connect to scott identified by tiger using 'orcl';

Database link created.

SQL> select * from dba_db_links;

OWNER        DB_LINK       USERNAME       HOST               CREATED

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

PUBLIC         PPS                SCOTT               orcl                 2014-11-24 16:43:54

PPA             TPS                  SCOTT               orcl                2014-11-24 16:43:39

现在开始来修改密码，可以选择删除dbalink后重建db link的方式。也可以直接修改。

修改public db link密码，在sys用户下执行：

SQL>  alter public database link pps connect to scott identified by oracle;

Database link altered.

SQL> select count(*) from tab@pps;

COUNT(*)

----------

4

修改private db link的密码

SQL> alter database link tps connect to scott identified by oracle;

alter database link tps connect to scott identified by oracle

*

ERROR at line 1:

ORA-01031: insufficient privileges

权限不足的，因此授予权限，登陆dba用户

SQL> grant alter database link to ppa;

Grant succeeded.

SQL> alter database link tps connect to scott identified by oracle;

Database link altered.

SQL> select count(*) from tab@tps;

COUNT(*)

----------

4

完成。