*  [[https://oracle-base.com/articles/misc/os-authentication|Create external user (using OPS$)]]
  *  [[Create User like...]]
==== Users created when installing Oracle 11.2.0.4 Standard Edition ====
<code>
select username from dba_users order by 1;

USERNAME
------------------------------
ANONYMOUS
APEX_030200
APEX_PUBLIC_USER
APPQOSSYS
CTXSYS
DBSNMP
DIP
EXFSYS
FLOWS_FILES
MDSYS
MGMT_VIEW
ORACLE_OCM
ORDDATA
ORDPLUGINS
ORDSYS
OUTLN
OWBSYS
OWBSYS_AUDIT
SI_INFORMTN_SCHEMA
SYS
SYSMAN
SYSTEM
WMSYS
XDB
XS$NULL

25 rows selected.
</code>

==== Users created when installing Oracle 11.2.0.4 Enterprise Edition ====
<code>
select username from dba_users order by 1;

USERNAME
------------------------------
ANONYMOUS
APEX_030200
APEX_PUBLIC_USER
APPQOSSYS
CTXSYS
DBSNMP
DIP
EXFSYS
FLOWS_FILES
MDDATA
MDSYS
MGMT_VIEW
OLAPSYS
ORACLE_OCM
ORDDATA
ORDPLUGINS
ORDSYS
OUTLN
OWBSYS
OWBSYS_AUDIT
SI_INFORMTN_SCHEMA
SPATIAL_CSW_ADMIN_USR
SPATIAL_WFS_ADMIN_USR
SYS
SYSMAN
SYSTEM
WMSYS
XDB
XS$NULL

29 rows selected.
</code>

==== Show list of database users and their roles / privileges ====
<code>
select
  lpad(' ', 2*level) || granted_role "User, his roles and privileges"
from
  (
  /* THE USERS */
    select
      null     grantee,
      username granted_role
    from
      dba_users
  /* THE ROLES TO ROLES RELATIONS */
  union
    select
      grantee,
      granted_role
    from
      dba_role_privs
  /* THE ROLES TO PRIVILEGE RELATIONS */
  union
    select
      grantee,
      privilege
    from
      dba_sys_privs
  )
start with grantee is null
connect by grantee = prior granted_role;
</code>
==== Rename an Oracle schema without exporting and importing all schema data ====
If the user is very large, it can take a very long time to use the standard way expdp / impdp.\\
It can be done more efficiently using transportable tablespaces technique to remap the schema.
  *  [[https://pierreforstmanndotcom.wordpress.com/2015/02/27/how-to-rename-an-oracle-schema-without-exporting-and-importing-all-schema-data/|Rename an Oracle Schema using Transportable Tablespace]]
Basic steps
  *  check with DBMS_TTS.TRANSPORT_SET_CHECK that tablespace can be transported
  *  Make the tablespace read only
  *  Export tablespace metadata
  *  Drop the tablespace but keep its datafiles
  *  Create the new user account representing the renamed schema and grant needed privileges
  *  Import tablespace metadata and rename schema objects owner at the same time
  *  Make tablespce read write
  *  Set password for new user account and set default tablespace for this new account
  *  Drop old user account representing the schema before renaming

==== Rename an Oracle schema using Rodrigo Jorge's clever method ====
Essentially performs a network datapump from PL/SQL using a database link back to the same database so no intermediate dump file is necessary.
  * https://www.dbarj.com.br/en/2014/11/rename-schema-oracle-11g-loopback-dblink/

=== Unsupported way (Oracle have closed this loophole as of 19.9!) ===
An unsupported workaround to rename a schema is to simply update the username in sys.user$ and restart the database.
<code>
select user# from sys.user$ where name = 'EPK';
</code>
<code>
   USER_ID
----------
       172
</code>
<code>
update sys.user$ set name = 'KPK' where user# = 172;
</code>
<code>
1 row updated.
</code>

==== Create external user ====
=== Check the authentification prefix ===
<code>
SQL> show parameter authent

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
os_authent_prefix                    string      ops$
SQL>
</code>
=== On Unix... ===
<code>
create user ops$oracle identified externally;
grant create session to ops$oracle;
</code>
=== On Windows... ===
Watch out on Windows - the domain name needs to be included!
<code>
create user "ops$domainname.com\\oracle" identified externally;
grant create session to "ops$domainname.com\\oracle";
</code>
Additionally, the following option must be set in "%ORACLE_HOME%\
etwork\\admin\\sqlnet.ora"\\
If this is not present, you will not be able to connect as sysdba
<code>
SQLNET.AUTHENTICATION_SERVICES=(NTS)
</code>