how to stop / start / open an Oracle pluggable container database

alter pluggable database orclpdb open;

Of course you will want to connect as sys “sqlplus / as sysdba” or equivalent to issue this command.

Here is a link to Oracle’s views on pluggable DBs:

https://docs.oracle.com/database/121/ADMIN/cdb_mon.htm#ADMIN13933

SELECT * FROM DBA_PDBS;