1、查找最近一天内，最消耗CPU的SQL语句

SELECT ASH.INST_ID,
       ASH.SQL_ID,
       (SELECT VS.SQL_TEXT
          FROM GV$SQLAREA VS
         WHERE VS.SQL_ID = ASH.SQL_ID
           AND ASH.INST_ID = VS.INST_ID) SQL_TEXT,
       ASH.SQL_CHILD_NUMBER,
       ASH.SQL_OPNAME,
       ASH.SESSION_INFO,
       COUNTS,
       PCTLOAD * 100 || '%' PCTLOAD
  FROM (SELECT ASH.INST_ID,
               ASH.SQL_ID,
               ASH.SQL_CHILD_NUMBER,
               ASH.SQL_OPNAME,
               (ASH.MODULE || '--' || ASH.ACTION || '--' || ASH.PROGRAM || '--' ||
               ASH.MACHINE || '--' || ASH.CLIENT_ID || '--' ||
               ASH.SESSION_TYPE) SESSION_INFO,
               COUNT(*) COUNTS,
               ROUND(COUNT(*) / SUM(COUNT(*)) OVER(), 2) PCTLOAD,
               DENSE_RANK() OVER(ORDER BY COUNT(*) DESC) RANK_ORDER
          FROM GV$ACTIVE_SESSION_HISTORY ASH
         WHERE ASH.SESSION_TYPE <> 'BACKGROUND'
           AND ASH.SESSION_STATE = 'ON CPU'
           AND SAMPLE_TIME > SYSDATE - 1
         GROUP BY ASH.INST_ID,
                  ASH.SQL_ID,
                  ASH.SQL_CHILD_NUMBER,
                  ASH.SQL_OPNAME,
                  (ASH.MODULE || '--' || ASH.ACTION || '--' || ASH.PROGRAM || '--' ||
                  ASH.MACHINE || '--' || ASH.CLIENT_ID || '--' ||
                  ASH.SESSION_TYPE)) ASH
 WHERE RANK_ORDER <= 10
 ORDER BY COUNTS DESC;

2、查找最近一天内，最消耗CPU的会话

SELECT SESSION_ID, COUNT(*)
  FROM V$ACTIVE_SESSION_HISTORY V
 WHERE V.SESSION_STATE = 'ON CPU'
   AND V.SAMPLE_TIME > SYSDATE - 1
 GROUP BY SESSION_ID
 ORDER BY COUNT(*) DESC;

3、查找最近一天内，最消耗资源的会话

SELECT ASH.SESSION_ID,
       ASH.SESSION_SERIAL#,
       ASH.USER_ID,
       ASH.PROGRAM,
       SUM(DECODE(ASH.SESSION_STATE, 'ON CPU', 1, 0)) "CPU",
       SUM(DECODE(ASH.SESSION_STATE, 'WAITING', 1, 0)) -
       SUM(DECODE(ASH.SESSION_STATE,
                  'WAITING',
                  DECODE(ASH.WAIT_CLASS, 'USER I/O', 1, 0),
                  0)) "WAITING",
       SUM(DECODE(ASH.SESSION_STATE,
                  'WAITING',
                  DECODE(ASH.WAIT_CLASS, 'USER I/O', 1, 0),
                  0)) "IO",
       SUM(DECODE(ASH.SESSION_STATE, 'ON CPU', 1, 1)) "TOTAL"
  FROM V$ACTIVE_SESSION_HISTORY ASH
 WHERE ASH.SAMPLE_TIME > SYSDATE - 1
 GROUP BY ASH.SESSION_ID, ASH.USER_ID, ASH.SESSION_SERIAL#, ASH.PROGRAM
 ORDER BY SUM(DECODE(ASH.SESSION_STATE, 'ON CPU', 1, 1));