sql / as sysdba

SELECT SID, SERIAL#, USERNAME, STATUS FROM V$SESSION WHERE USERNAME IS NOT NULL;

SHUTDOWN IMMEDIATE

sql / as sysdba

STARTUP

STARTUP MOUNT

STARTUP NOMOUNT

ALTER DATABASE MOUNT;

ALTER DATABASE OPEN;

show pdbs

ALTER PLUGGABLE DATABASE PDB1 OPEN;

show pdbs

STARTUP RESTRICT

ALTER SYSTEM ENABLE RESTRICTED SESSION;