ORA-39213: Metadata processing is not available

#sqlplus / as sysdba
SQL> execute sys.dbms_metadata_util.load_stylesheets;

Rename oracle user

c>sqlplus                                               
 c>user-name:sys as sysdba                                
 c>password:sys 
 sql>show user; 
SQL> select user#,NAME from SYS.user$ WHERE NAME='TEST';

USER# NAME
---------- ------------------------------
*93* TEST

SQL> UPDATE USER$ SET NAME='NEW_SCHEMA_NAME' WHERE USER#=93;

or using pupm:

impdp userid=host1/password4sk directory=tmp dumpfile=old_schema_to_remap remap_schema=HOST_USER:host1(new) LOGFILE=imp_schema_to_remap.log

How to find oracle service name

select value from v$parameter where name='service_names'

HOW TO CHANGE PDB$SEED RESTRICTED YES TO NO

> show pdbs;
>select logins from v$instance;

LOGINS
----------
RESTRICTED

> alter system disable restricted session;

System altered.

> select logins from v$instance;

LOGINS
----------
ALLOWED

> show pdbs;

How to open PDB$SEED database

SQL> conn / as sysdba
Connected.
SQL> select status from v$instance;
STATUS
------------
MOUNTED
   

SQL> alter database mount;
Database altered.
OR
SQL> alter database open;
Database altered.  

SQL> select status from v$instance;
STATUS
------------
OPEN 

SQL> show pdbs;
         2 PDB$SEED                       READ ONLY  NO
         3 TESCOPDBS                      MOUNTED
         4 UKAPEXTEST                     MOUNTED
         5 ORDERPDBS                      MOUNTED
         6 UKTEST                         MOUNTED  

SQL> alter pluggable database all open;
     Pluggable database altered.