oracle中查找执行效率低下的SQL

v$sqltext：存储的是完整的SQL,SQL被分割 v$sqlarea：存储的SQL 和一些相关的信息，比如累计的执行次数，逻辑读，物理读等统计信息（统计） v$sql：内存共享SQL区域中已经解析的SQL语句。（即时） selectopname,target,to_char(start_time,'yyyy-mm-ddhh24:m

v$sqltext：存储的是完整的SQL,SQL被分割

v$sqlarea：存储的SQL 和一些相关的信息，比如累计的执行次数，逻辑读，物理读等统计信息（统计）

v$sql：内存共享SQL区域中已经解析的SQL语句。（即时）

select opname, target, to_char(start_time, 'yyyy-mm-dd hh24:mi:ss') start_time, elapsed_seconds elapsed,

executions execs, buffer_gets/decode(executions, 0, 1, executions) bufgets, module, sql_text

from v$session_longops sl, v$sqlarea sa

where sl.sql_hash_value = sa.hash_value

and upper(substr(module, 1, 4)) <> 'RMAN'

and substr(opname, 1, 4 ) <> 'RMAN'

and sl.start_time > trunc(sysdate)

order by start_time;

根据sid查找完整sql语句：

select sql_text from v$sqltext a where a.hash_value = (select sql_hash_value from v$session b where b.sid = '&sid' )
order by piece asc

select a.CPU_TIME,--CPU时间 百万分之一（微秒）
a.OPTIMIZER_MODE,--优化方式
a.EXECUTIONS,--执行次数
a.DISK_READS,--读盘次数
a.SHARABLE_MEM,--占用shared pool的内存多少
a.BUFFER_GETS,--读取缓冲区的次数
a.COMMAND_TYPE,--命令类型(3:select,2:insert;6:update;7delete;47:pl/sql程序单元)
a.SQL_TEXT,--Sql语句
a.SHARABLE_MEM,
a.PERSISTENT_MEM,
a.RUNTIME_MEM,
a.PARSE_CALLS,
a.DISK_READS,
a.DIRECT_WRITES,
a.CONCURRENCY_WAIT_TIME,
a.USER_IO_WAIT_TIME
from SYS.V_$SQLAREA a
WHERE PARSING_SCHEMA_NAME = 'CHEA_FILL'--表空间
order by a.CPU_TIME desc

引用：http://jenniferok.iteye.com/blog/700985

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：内存共享SQL区域中已经解析的SQL语句。（即时）

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;

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;

v$sqlarea字段定义：http://happyhou.blog.sohu.com/60494432.html