我们知道Oracle Database 12c中用户分为COMMON_USERS 和 LOCAL_USERS两种，其中COMMON_USERS缺省以”C##”开头 ，其实这是受一个隐含参数控制的，即 _common_user_prefix
我们可以定制COMMON USER的前缀，下面咱们测试下：
[oracle@lunar ~]$ sqlplus / as sysdba
SQL*Plus: Release 12.1.0.1.0 Production on Thu Aug 29 21:25:56 2013
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Advanced Analytics
and Real Application Testing options
SYS@lunarbb>show con_name
CON_NAME
------------------------------
CDB$ROOT
SYS@lunarbb>show parameter spfile
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string +DATA/lunarbb/spfilelunarbb.or
a
SYS@lunarbb>col KSPPINM for a30
SYS@lunarbb>col ksppstvl format a15
SYS@lunarbb>col KSPPDESC for a55
SYS@lunarbb>select ksppinm, ksppstvl, KSPPDESC
2 from x$ksppi pi, x$ksppcv cv
3 where cv.indx=pi.indx and pi.ksppinm like '\_%' escape '\'
4 and pi.ksppinm like '%common%';
KSPPINM KSPPSTVL KSPPDESC
------------------------------ --------------- -------------------------------------------------------
_eliminate_common_subexpr TRUE enables elimination of common sub-expressions
_dump_common_subexpressions FALSE dump common subexpressions
_common_data_view_enabled TRUE common objects returned through dictionary views
_common_user_prefix C## Enforce restriction on a prefix of a Common User/Role/Profile name
Elapsed: 00:00:00.01
SYS@lunarbb>
SYS@lunarbb>conn c##lunar/lunar
Connected.
C##LUNAR@lunarbb>create pfile='/tmp/pfile.bak' from spfile;
create pfile='/tmp/pfile.bak' from spfile
*
ERROR at line 1:
ORA-01031: insufficient privileges
Elapsed: 00:00:00.00
C##LUNAR@lunarbb>conn c##lunar/lunar as sysdba
Connected.
SYS@lunarbb>create pfile='/tmp/pfile.bak' from spfile;
File created.
Elapsed: 00:00:00.12
SYS@lunarbb>
[oracle@lunar ~]$ tail /tmp/pfile.bak
*.query_rewrite_enabled='TRUE'
*.remote_login_passwordfile='EXCLUSIVE'
*.resource_manager_plan='SCHEDULER[0x420F]:DEFAULT_MAINTENANCE_PLAN'
*.result_cache_max_size=1560K
*.sga_max_size=330M# internally adjusted
*.sga_target=330M
*.shared_pool_size=160M
*.skip_unusable_indexes=TRUE
*.undo_tablespace='UNDOTBS1'
*._common_user_prefix='L##'
[oracle@lunar ~]$
SYS@lunarbb>shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@lunarbb>startup pfile=/tmp/pfile.bak
ORACLE instance started.
Total System Global Area 346562560 bytes
Fixed Size 2288240 bytes
Variable Size 297797008 bytes
Database Buffers 37748736 bytes
Redo Buffers 8728576 bytes
Database mounted.
Database opened.
SYS@lunarbb>
SYS@lunarbb>conn c##lunar/lunar
Connected.
C##LUNAR@lunarbb>conn L##lunar/lunar
ERROR:
ORA-01017: invalid username/password; logon denied
Warning: You are no longer connected to ORACLE.
C##LUNAR@lunarbb>
C##LUNAR@lunarbb>conn / as sysdba
Connected.
SYS@lunarbb>
SYS@lunarbb>CREATE USER L##lunar IDENTIFIED BY lunar;
User created.
Elapsed: 00:00:00.80
SYS@lunarbb>grant dba,sysdba,connect,resource to L##lunar;
Grant succeeded.
Elapsed: 00:00:00.17
SYS@lunarbb>
SYS@lunarbb>conn L##lunar/lunar
Connected.
L##LUNAR@lunarbb>conn L##lunar/lunar as sysdba
Connected.
SYS@lunarbb>
SYS@lunarbb>show parameter common
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
_common_data_view_enabled boolean TRUE
_common_user_prefix string L##
_eliminate_common_subexpr boolean TRUE
SYS@lunarbb>
