[oracle@db12cr2 bin]$ sqlplus system/aaaaaa

sql*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 06:43:38 2017

Copyright (c) 1982,2016,Oracle.  All rights reserved.

Last Successful login time: Mon Mar 13 2017 18:21:44 +08:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

sql>  show parameter case 


NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
sec_case_sensitive_logon	     boolean	 TRUE ------------->>>>>>>>>>>>>默认值
sql> 
sql> 
sql> alter system set sec_case_sensitive_logon=false;------------->>>>>>>>>>>>>改为false

System altered.

sql> show parameter case 

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
sec_case_sensitive_logon	     boolean	 FALSE
sql> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
[oracle@db12cr2 bin]$ sqlplus system/aaaaaa    ------------->>>>>>>>>>>>>然后用正确的密码就不能登录了.

sql*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 06:44:19 2017

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

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


Enter user-name: ^C
[oracle@db12cr2 bin]$ sqlplus / as sysdba

sql*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 06:44:43 2017

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


Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

sql> show parameter case

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
sec_case_sensitive_logon	     boolean	 FALSE
sql> alter system set sec_case_sensitive_logon=true;------------->>>>>>>>>>>>>改为true

System altered.

sql> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
[oracle@db12cr2 bin]$ sqlplus system/aaaaaa  ------------->>>>>>>>>>>>>然后用正确的密码就能登录了!!!!

sql*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 06:45:17 2017

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

Last Successful login time: Wed Mar 15 2017 06:43:39 +08:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

sql> 

sql> alter system set sec_case_sensitive_logon=false; 

System altered.

sql> conn c##test/db12c
Connected.
sql> show user
USER is "C##TEST"
sql> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
[oracle@db12cr2 bin]$ sqlplus c##test/db12c------>>>小写的C,能登陆成功.

sql*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 06:35:34 2017

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

Last Successful login time: Wed Mar 15 2017 06:35:08 +08:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

sql> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
[oracle@db12cr2 bin]$ sqlplus c##test/db12C------>>>大写的C,能登陆成功,说明密码不再区分大小写.

sql*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 06:35:54 2017

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

Last Successful login time: Wed Mar 15 2017 06:35:34 +08:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

sql> show user
USER is "C##TEST"
sql> ----->>>>>C##test用户能用密码登录成功...