Recreate objects using dbms metadata.get ddl

Recreate all the users (including grants) in a database

 select dbms_metadata.get_ddl('USER', username) || '/' ddl
 from dba_users
 union all
 select dbms_metadata.get_granted_ddl('ROLE_GRANT', username) || '/' ddl
 from dba_users
 union all
 select dbms_metadata.get_granted_ddl('SYSTEM_GRANT', username) || '/' ddl
 from dba_users
 union all
 select dbms_metadata.get_granted_ddl('OBJECT_GRANT', username) || '/' ddl
 from dba_users;