【转载】查看最近的redo生成量

用下面的sql查看最近的redo生成量：

SELECT END_TIME,
       INSTANCE_NUMBER,
       round(redo_size/1024,2) redo_size_kb
FROM
  (SELECT /*+ RULE */ TO_CHAR(C.END_INTERVAL_TIME, 'YYYY-MM-DD HH24:MI') END_TIME,
                      A.INSTANCE_NUMBER INSTANCE_NUMBER,
                      CASE
                          WHEN SUM(A.VALUE-B.VALUE) > 0 THEN ROUND(SUM((A.VALUE-B.VALUE)/C.INTERVAL_2_S))
                          ELSE 0
                      END redo_size
   FROM DBA_HIST_SYSSTAT A, DBA_HIST_SYSSTAT B,
     (SELECT /*+ RULE */ SNAP_ID,
                         INSTANCE_NUMBER,
                         END_INTERVAL_TIME,
                         (CAST(END_INTERVAL_TIME AS DATE) - CAST(BEGIN_INTERVAL_TIME AS DATE))*86400 INTERVAL_2_S
      FROM DBA_HIST_SNAPSHOT
      WHERE --END_INTERVAL_TIME BETWEEN TO_DATE('201508211000', 'YYYYMMDDHH24MI') AND TO_DATE('201508211100', 'YYYYMMDDHH24MI')
      END_INTERVAL_TIME BETWEEN sysdate-30 AND sysdate
        --SNAP_ID in (31504,31505)
        ) C
   WHERE A.STAT_NAME IN ('redo size')
     AND B.STAT_ID = A.STAT_ID
     AND A.SNAP_ID = B.SNAP_ID + 1
     AND A.SNAP_ID = C.SNAP_ID
     AND B.DBID = A.DBID
     AND A.INSTANCE_NUMBER = B.INSTANCE_NUMBER
     AND A.INSTANCE_NUMBER = C.INSTANCE_NUMBER
     --AND A.INSTANCE_NUMBER = 1
   GROUP BY C.END_INTERVAL_TIME,A.INSTANCE_NUMBER
   )
ORDER BY 2,1;