In a multitenant environment,
a common user is a
database user whose identity and
password are known in the root and in every existing and future pluggable
database (PDB).
Hence common user and local user name cannot be same.
Lets proof this satement
SQL> alter system set "_common_user_prefix"=''
scope=spfile;
System altered.
SQL> create pfile from spfile;
File created.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
In pfile
ora12c._common_user_prefix=''
SQL> startup pfile='C:\app\XXXXXX\product\12.1.0\dbhome_1\database\INITora12c.ORA';
ORACLE instance started.
Total System Global Area 1068937216
bytes
Fixed Size 2410864 bytes
Variable Size 666896016 bytes
Database Buffers 394264576 bytes
Redo Buffers 5365760 bytes
Database mounted.
Database opened.
SQL>
SQL>
SQL> show con_name
CON_NAME
------------------------------
CDB$ROOT
SQL> create user demo identified by
demo;
User created.
SQL> select name,open_mode from
v$pdbs;
NAME OPEN_MODE
------------------------------
----------
PDB$SEED READ ONLY
PDBORA12C MOUNTED
SUBUPDB MOUNTED
TEST READ WRITE
SQL> alter session set
container=TEST;
Session altered.
SQL> show con_name
CON_NAME
------------------------------
TEST
SQL> create user demo identified by
demo;
create user demo identified by demo
*
ERROR at line 1:
ORA-01920: user name 'DEMO'
conflicts with another user or role name
SQL> show con_name
CON_NAME
------------------------------
TEST
SQL> create
user hello identified by hello;
User created.
SQL> show con_name
CON_NAME
------------------------------
CDB$ROOT
SQL> create
user hello identified by hello;
create user hello identified by hello
*
ERROR at line 1:
ORA-65048: error encountered when
processing the current DDL statement in
pluggable database TEST
ORA-01920: user name 'HELLO' conflicts
with another user or role name
