Oracle – Query para monitorar uso do Tablespace UNDO

Para monitorar o tamanho alocado e uso atual (em Mb) do tablespace de UNDO utilize a seguinte query

select a.tablespace_name, SIZEMB, USAGEMB, (SIZEMB – USAGEMB) FREEMB
from (select sum(bytes) / 1024 / 1024 SIZEMB, b.tablespace_name
from dba_data_files a, dba_tablespaces b
where a.tablespace_name = b.tablespace_name
and b.contents = ‘UNDO’
group by b.tablespace_name) a,
(select c.tablespace_name, sum(bytes) / 1024 / 1024 USAGEMB
from DBA_UNDO_EXTENTS c
where status <> ‘EXPIRED’
group by c.tablespace_name) b
where a.tablespace_name = b.tablespace_name;


So, what do you think ?