oracle 识别低效执行的SQL语句

SELECT EXECUTIONS , DISK_READS, BUFFER_GETS, 


ROUND((BUFFER_GETS-DISK_READS)/BUFFER_GETS,2) Hit_radio, 


ROUND(DISK_READS/EXECUTIONS,2) Reads_per_run, 


SQL_TEXT 


FROM V$SQLAREA 


WHERE EXECUTIONS>0 


AND BUFFER_GETS > 0 


AND (BUFFER_GETS-DISK_READS)/BUFFER_GETS < 0.8 


ORDER BY 4 DESC;