v$sesstat是子系统所有session的stat

v$mystat视图中只会有当前用户的会话信息，v$sesstat会有整个实例内所有会话信息。因此在v$sesstat中自然包括v&mystat的统计信息。

SQL> desc v$sysstat

Name                                      Null?    Type

----------------------------------------- -------- ----------------------------

 STATISTIC#                                         NUMBER

NAME                                               VARCHAR2(64)

 CLASS                                              NUMBER

VALUE                                              NUMBER

SQL> desc v$statname

Name                                      Null?    Type

----------------------------------------- -------- ----------------------------

 STATISTIC#                                         NUMBER

NAME                                               VARCHAR2(64)

 CLASS                                              NUMBER

v$statname视图中STATISTIC#与v$mystat,v$sesstat中STATISTIC#字段是相关联的。而NAME则是对应的英文信息，比如说要查某条DML语句所产生的redo信息。可以这样写:

select t.sid, t.value/1024/1024 size_m

from v$sesstat t, v$statname n

 where t.STATISTIC# = n.STATISTIC#

   and name = redo size

 order by 2;

select value

from v$mystat t, v$statname t1

 where t.STATISTIC# = t1.STATISTIC#

   and t1.NAME = redo size;