在oracle dataguard环境中,当主库修改密码之后,备库不会立即生效,需要flush shared pool之后才会生效
主库创建用户并尝试登录

[oracle@primary ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Sep 3 17:24:12 2019
Copyright (c) 1982, 2013, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options
SQL> select open_mode,database_role from v$database;
OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
READ WRITE           PRIMARY
SQL> create user xff identified by oracle;
User created.
SQL> grant dba to xff;
Grant succeeded.
SQL> conn xff/oracle
Connected.

备库登录信息

[oracle@standby ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Sep 3 17:17:47 2019
Copyright (c) 1982, 2013, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> select database_role,open_mode from v$database;
DATABASE_ROLE    OPEN_MODE
---------------- --------------------
PHYSICAL STANDBY READ ONLY WITH APPLY
[oracle@standby ~]$ ss
SQL*Plus: Release 11.2.0.4.0 Production on Tue Sep 3 17:25:58 2019
Copyright (c) 1982, 2013, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> conn xff/oracle
Connected.

主库修改密码

[oracle@primary ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Sep 3 17:17:47 2019
Copyright (c) 1982, 2013, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>  alter user xff identified by xff;
User altered.
SQL> conn xff/xff
Connected.

备库尝试登录

SQL> conn xff/xff;
ERROR:
ORA-01017: invalid username/password; logon denied
Warning: You are no longer connected to ORACLE.
SQL> conn xff/oracle
Connected.

备库原密码可以登录修改之后的密码无法登录
备库刷新shared pool,新密码登录成功

SQL> conn / as sysdba
Connected.
SQL> alter system flush shared_pool;
System altered.
SQL> conn xff/oracle
ERROR:
ORA-01017: invalid username/password; logon denied
Warning: You are no longer connected to ORACLE.
SQL> conn xff/xff
Connected.