10:59:51 7 FROM dba_tablespaces
11:00:01 8 where tablespace_name=(select upper(value) from v$parameter where name='undo_tablespace'));
BYTES
----------
87293952
Elapsed: 00:00:00.07
11:00:45 SYS@ prod>
11:00:45 SYS@ prod>select (UR * (UPS * DBS))/1024/1024 AS "BYTES"
11:01:42 2 from (select value AS UR from v$parameter where name='undo_retention'),
11:01:42 3 (select undoblks/((end_time-begin_time)*900) as UPS
11:01:42 4 FROM v$undostat
11:01:42 5 where undoblks=(select max(undoblks) from v$undostat)),
11:01:42 6 (select block_size as DBS
11:01:42 7 FROM dba_tablespaces
11:01:42 8 where tablespace_name=(select upper(value) from v$parameter where name='undo_tablespace'));
BYTES
----------
83.25
Elapsed: 00:00:00.10
11:01:44 SYS@ prod>
以上部分内容参考了《Oracle DBA实战攻略》书中的内容，这里表示感谢！