oracle@wocdb6 ~]$ sqlplus wa/Sx

SQL*Plus: Release 11.2.0.4.0 Production on Thu Jul 23 09:47:40 2020

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

ERROR:
ORA-01017: invalid username/password; logon denied

PROGRAM         USERNAME   OSUSER    SQL_ID      MACHINE   STATUS S_TIME    EVENT
------------------------- ----- ------- -------------- -------- -------------- ---------
JDBC Thin Client           admin           osx-scp001xx ACTIVE        library cache lock
JDBC Thin Client           admin           osx-scp001xx ACTIVE        library cache lock
JDBC Thin Client           admin           osx-scp001xx ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock
gate_svr@localhost (TNS V  root               localhost    ACTIVE        library cache lock

检查RAC 2个节点，ACTIVE的Session都是啥event,可以发现是library cache lock 
1. 会话等待事件是library cache lock
2. ???USERNAME 都是null?
3. 为啥没有library cache pin ? or 其它的等待事件！！！

SQL> begin
  2   dbms_workload_repository.create_snapshot();
  3   end;
  4  /
PL/SQL procedure successfully completed.

观察 connect xxx   99%!!!

--关闭错误输入密码时的密码延迟验证特性，避免用户持续输入错误密码时产生大量的library cache lock等待，严重时使数据库完全不能登录

alter system set event=‘28401 trace name context forever,level 1‘,‘10949 trace name context forever,level 1‘ scope=spfile;

In 11g there is an intentional delay between allowing failed logon
attempts to retry. For some specific application types this can cause
a problem as the row cache entry is locked for the duration of the
delay . This can lead to excessive row cache lock waits for DC_USERS
for specific users / schemas .
 
This "fix" allows the logon delay to be disabled in 11.2.0.1 onwards
by setting event 28401 in the init.ora.
eg:
    event="28401 trace name context forever, level 1" # disable logon delay.
This "event" will disable the logon sleep delay system-wide, 
ie. it will affect all user accounts, system-wide, and so should be used
    with extreme caution.

观察上述信息，可以了解到问题的原因，需要确认！
1.关闭监听，组织新的会话连接；
$ srvctl stop listener
2.杀掉已连接的会话

select ‘alter system kill session ‘‘‘||sid||‘,‘||serial#||‘‘‘ immediate;‘ as "sql_text" from v$session where event=‘library cache lock‘;

3.测试确认是密码错误【已掌握密码】
会话均不存在后，测试登录是等待一段时间可以出现报错信息，而非Hang住

ERROR:
ORA-01017: invalid username/password; logon denied

  4.修改密码即可！

SQL> alter user wxx identified by "Sxx1";

  5.启动监听

$ srvctl start listener

！如果想后续再次出现同样的问题，可以设置上述Event，本次由于是稳定的生产环境，极少出现，因此并未设置event.