Oracle has introduced multi-tenant architecture in 12c. With this , we will have an instance ( Single Instance) , multiple instances ( RAC) will be hosting multiple pluggable databases ( PDBs) with in a container database ( CDB).
Please note that the CDB/PDB is extra licensing option . With the regular license , we can have a CDB with only one PDB.
Accordingly , there are changes to how users are maintained in 12c. There are two type of users.
a) Common User
b) Local User
In short , common user is for all PDBs and Local user is local to a PDB.
There are few rules / restrictions in creating a common user.
One of them being , the username has to be prefixed with ( c##) .
However , this can be circumvented . But I would recommend against against this practice, as this is not ( likely ) supported by oracle .
Here is an example .
SQL> show con_name
CON_NAME
------------------------------
CDB$ROOT
SQL> create user c##zahir identified by ZahirPassword container=all;
User created.
As you can see, common user ( c##zahir) was created sucessfully .
Let us try , by removing c##.
SQL> create user zahirm identified by ZahirPassword container=all;
create user zahirm identified by ZahirPassword container=all
*
ERROR at line 1:
ORA-65096: invalid common user or role name
Let us set the UNDOCUMENTED parameter to true .
Being this is undocumented parameter ; as like many Oracle professionals ,
I would not recommend with meddling with these parameters unless otherwise directed by Oracle support.
Note : This parameter also needed , when you need to create a CDB from sqlplus.
SQL> alter session set "_oracle_script"=true;
Session altered.
SQL> create user zahirm identified by ZahirPassword container=all;
User created.
Voila . The user was created .
Comments Welcome.
