[oracle@prim ~]$ sqlplus / as sysdba
SQL*Plus: Release 19.0.0.0.0 - Production on Wed Oct 11 14:46:12 2023
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle.  All rights reserved.
Connected to an idle instance.
SQL>
SQL>
SQL> startup
ORACLE instance started.

Total System Global Area 1744828000 bytes
Fixed Size                  9135712 bytes
Variable Size             452984832 bytes
Database Buffers         1275068416 bytes
Redo Buffers                7639040 bytes
Database mounted.
Database opened.
SQL> SQL> SQL>
SQL>
SQL> select name, open_mode from v$database;

NAME      OPEN_MODE
--------- --------------------
TESTDB    READ WRITE
SQL>
SQL> show pdbs;

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 PDBDB                          MOUNTED
         4 ABC                            MOUNTED
SQL>
SQL>
SQL>
create pluggable database pdb1 admin user testuser identified by "testuser"
default tablespace users
datafile '/data/app/oracle/oradata/TESTDB/users02.dbf'
size 10M AUTOEXTEND ON
FILE_NAME_CONVERT=('/data/app/oracle/oradata/TESTDB/pdbseed','/data/app/oracle/oradata/TESTDB/PDB1');

SQL>   2    3    4    5

Pluggable database created.
SQL> show pdbs;

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 PDBDB                          MOUNTED
         4 ABC                            MOUNTED
         5 PDB1                           MOUNTED
SQL>
SQL>
SQL> alter pluggable database pdb1 open;
Pluggable database altered.
SQL>
SQL>