Hit_radio和Reads_per_run是什么意思呢？

Question

从V$SQLAREA中查询最占用资源的查询：SELECT EXECUTIONS, DISK_READS, BUFFER_GETS,
   ROUND ((BUFFER_GETS-DISK_READS)/BUFFER_GETS, 2) Hit_radio,
   ROUND (DISK_READS/EXECUTIONS, 2) Reads_per_run,
   SQL_TEXT
FROM   V$SQLAREA
WHERE  EXECUTIONS>0
AND     BUFFER_GETS > 0 
AND (BUFFER_GETS-DISK_READS)/BUFFER_GETS < 0.8 
ORDER BY 4 DESC其中，Hit_radio和Reads_per_run是什么意思呢？

Answer 1

Hit_radio --在内存中的命中率
Reads_per_run --每次执行对磁盘的读取数

Answer 2

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