如何查找消耗资源较大的SQL

对于优化来讲，查找消耗资源较大的SQL至关重要，下面介绍几个之前用到的SQL。1.从V$SQLAREA中查询最占用资源的查询。select b.username username,a.disk_reads reads,    a.executions exec,a.disk_reads/decode(a.executions,0,1,a.executions) rds_exec_ratio,    a.sql_text Statement    from v$sqlarea a,dba_users b    where a.parsing_user_id=b.user_id    and a.disk_reads > 100000    order by a.disk_reads desc;    用buffer_gets列来替换disk_reads列可以得到占用最多内存的sql语句的相关信息。V$SQL是内存共享SQL区域中已经解析的SQL语句。2.列出使用频率最高的5个查询：select sql_text,executions    from (select sql_text,executions,    rank() over    (order by executions desc) exec_rank    from v$sql)    where exec_rank <=5;    3.消耗磁盘读取最多的sql top5：select disk_reads,sql_text    from (select sql_text,disk_reads,    dense_rank() over    (order by disk_reads desc) disk_reads_rank    from v$sql)    where disk_reads_rank <=5;    找出需要大量缓冲读取（逻辑读）操作的查询：select buffer_gets,sql_text    from (select sql_text,buffer_gets,    dense_rank() over    (order by buffer_gets desc) buffer_gets_rank    from v$sql)    where buffer_gets_rank<=5;