Use of PDB save or discard State for pluggable database in Oracle CDB

To open all PDBs at CDB startup, create the following trigger in CDB:

Trigger to Open all the pluggable database with the CDB database:

CREATE TRIGGER open_all_pdbs
  AFTER STARTUP ON DATABASE
BEGIN
   EXECUTE IMMEDIATE 'ALTER PLUGGABLE DATABASE ALL OPEN';
END ;
/

Use of save or discard state of the open mode of a PDB

SQL> ALTER PLUGGABLE DATABASE PDBP2 OPEN;
Pluggable Database opened.

SQL> select CON_ID, NAME, OPEN_MODE, RESTRICTED, OPEN_TIME  from gv$containers;
CON_ID NAME                 OPEN_MODE  RESTRICTED OPEN_TIME
------ ------------------- ---------- ---------- -----------------------------
    1  CDB$ROOT             READ WRITE NO         08-OCT-24 11.14.42.775 AM +01:00
    2  PDB$SEED             READ ONLY  NO         08-OCT-24 11.14.42.873 AM +01:00
    3  PDB1                 READ WRITE NO         08-OCT-24 11.28.26.830 AM +01:00
    4  PDB2                 MOUNTED

SQL> select con_name, state from dba_pdb_saved_states;
no rows selected

SQL> ALTER PLUGGABLE DATABASE PDBP2 SAVE STATE;
Pluggable database altered.

SQL> select con_name, state from dba_pdb_saved_states;
CON_NAME      STATE
------------- --------------
PDB2          OPEN

Only the save state is recorded on DBA_PDB_SAVED_STATES.

SQL> ALTER PLUGGABLE DATABASE PDB2 DISCARD STATE;
Pluggable database altered.

SQL> select con_name, state from dba_pdb_saved_states;
no rows selected