PLSQL_低效SQL的识别和查询汇总（案例）

2014-12-18 Created By BaoXinjian

1. 查找排序最多的SQL

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  SELECT HASH_VALUE, SQL_TEXT, SORTS, EXECUTIONS FROM V$SQLAREA ORDER BY   SORTS DESC;

2.查找磁盘读写最多的SQL

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SELECT   *

  FROM   (  SELECT sql_text, disk_reads "total disk", executions "total exec", disk_reads / executions "disk/exec" FROM v$sql WHERE   executions > 0 AND is_obsolete = 'N'

          ORDER BY   4 DESC) WHERE   ROWNUM < 11;

 

3.查找工作量最大的SQL(实际上也是按磁盘读写来排序的)

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  SELECT   SUBSTR (TO_CHAR (s.pct, '99.00'), 2) || '%' load, s.executions executes, p.sql_text FROM   (SELECT address, disk_reads, executions, pct, RANK () OVER (ORDER BY disk_reads DESC) ranking FROM   (SELECT address, disk_reads, executions, 100 * ratio_to_report (disk_reads) OVER () pct FROM sys.v_$sql WHERE   command_type != 47) WHERE   disk_reads > 50 * executions) s, sys.v_$sqltext p WHERE   s.ranking <= 5 AND p.address = s.address ORDER BY   1, s.address, p.piece;

 

4. 用下列SQL工具找出低效SQL

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  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;

 

Thanks and Regards

转载：一江水 - http://www.cnblogs.com/rootq/archive/2009/12/24/1631415.html