Search notes:

SQL*PLUS: SHOW PDBS

show pdbs display the names, ids, mode and restriction status of the Pluggable Databases in the consolidated database to which the user is connected. 
$ sqlplus / as sysdba
   …
SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 PDBTQ84                        READ WRITE NO

See also

SQL*Plus, the show command.
show con_id and show con_name (Only available with SYSDBA privileges, otherwise SP2-0382: The SHOW PDBS command is not available is thrown).

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:78 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(78): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/developm...', 1741096858, '18.217.103.111', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/development/databases/Oracle/SQL-Plus/show/pdbs(49): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78