SQL classification, user properties

See what roles there are

select * from user_role_privs;

View your own roles and permissions
select * from role_sys_privs;

The modification user is locked （ Non locking ） state , Locked status is unable to log in
alter user user name account lock|unlock;

Query the user
select * from all_users;

Ordinary users
sqlplus user name / password ;

System administrator login , Identity must be specified ,as sysdba perhaps as sysoper, You can log in normally without entering a password
sqlplus sys/ as sysdba;