SQL> select extent_management from dba_tablespaces where tablespace_name='RBS';

EXTENT_MAN
----------
DICTIONARY

SQL> 

SQL> alter rollback segment R09 storage(maxextents 32764);

Rollback segment altered.

SQL> alter rollback segment R09 storage(maxextents 32765);

Rollback segment altered.

SQL> alter rollback segment R09 storage(maxextents 32766);
alter rollback segment R09 storage(maxextents 32766)
                                              *
ERROR at line 1:
ORA-02221: invalid MAXEXTENTS storage option value


SQL>