don't the users SYS and SYSTEM share the table dba_users?
Local users created in a pluggable database are not visible in other containers through DBA_USERS. You can query all users from all open pluggable databases in the root container through CDB_USERS.

Overview of Commonality in a CDB

SQL&gt; show con_name pdbs

CON_NAME
------------------------------
CDB$ROOT

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 SAMPLE                         READ WRITE NO
         5 BENCHMARK                      READ WRITE NO

SQL&gt;  conn sys/Oracle123@o7ca1-vip/SAMPLE as sysdba
Connected.
SQL&gt; create user user_created_by_sys identified by 1;

User created.

SQL&gt; conn system/Oracle123@o7ca1-vip/BENCHMARK
Connected.
SQL&gt; create user user_created_by_system identified by 1;

User created.

SQL&gt; select username from dba_users where username like 'USER_CREATED%';

USERNAME
--------------------------------------------------------------------------------------------------------------------------------
USER_CREATED_BY_SYSTEM

SQL&gt; conn sys/Oracle123@o7ca1-vip/SAMPLE as sysdba
Connected.
SQL&gt; select username from dba_users where username like 'USER_CREATED%';

USERNAME
--------------------------------------------------------------------------------------------------------------------------------
USER_CREATED_BY_SYS

SQL&gt; conn / as sysdba
Connected.
SQL&gt; select username from dba_users where username like 'USER_CREATED%';

no rows selected

SQL&gt; select con_id, username from cdb_users where username like 'USER_CREATED%';

    CON_ID USERNAME
---------- --------------------------------------------------------------------------------------------------------------------------------
         3 USER_CREATED_BY_SYS
         5 USER_CREATED_BY_SYSTEM