Permissions for Oracle Users ____oracle

DBA: With full privileges, the system has the highest privileges, and only DBAs can create the database structure. 
RESOURCE: Users with RESOURCE permissions can create entities only and cannot create database structures. 
Connect: Users who have CONNECT permissions can only log on to Oracle and cannot create entities and cannot create database configurations. 
for ordinary users: Grant Connect, resource permissions. 
for DBA Administration User: Grant Connect,resource, dba authority. A
normal user can have the same user rights as the system through authorization, but will never reach the same permissions as the SYS user, and the system user's permissions can be reclaimed.
query where the user has permissions:
             Sql> select * from Dba_role_privs; 
             Sql> select * from Dba_sys_privs; 
             Sql> select * from Role_sys_privs;
SYSDBA has the highest system privileges login to SYS
so you login as SYSDBA is logged  in sys so you set up a table in sys, and a normal user login cannot see the SYS table.