常用定位性能问题的sql

可以到v$sql中查询，比如以buffer_gets,executions,disk_reads等条件判断．


--值得怀疑的SQL




selectsubstr(to_char(s.pct,'99.00'),2)||'%'load,
       s.executions executes,
       p.sql_text
 from(selectaddress,
               disk_reads,
               executions,
               pct,
               rank()over(orderbydisk_readsdesc) ranking
         from(selectaddress,
                       disk_reads,
                       executions,
                      100*ratio_to_report(disk_reads)over() pct
                 fromsys.v_$sql
                wherecommand_type!=47)
        wheredisk_reads>50*executions) s,
       sys.v_$sqltext p
wheres.ranking<=5
  andp.address=s.address
orderby1, s.address, p.piece;
--逻辑读多的SQL
select*
 from(selectbuffer_gets, sql_text
         fromv$sqlarea
        wherebuffer_gets>500000
        orderbybuffer_getsdesc)
whererownum<=30;
--执行次数多的SQL
selectsql_text, executions
 from(selectsql_text, executionsfromv$sqlareaorderbyexecutionsdesc)
whererownum<81;
--读硬盘多的SQL
selectsql_text, disk_reads
 from(selectsql_text, disk_readsfromv$sqlareaorderbydisk_readsdesc)
whererownum<21;
--排序多的SQL
selectsql_text, sorts
 from(selectsql_text, sortsfromv$sqlareaorderbysortsdesc)
whererownum<21;
--分析的次数太多，执行的次数太少，要用绑变量的方法来写sql
setpagesize600;
setlinesize120;
selectsubstr(sql_text,1,80) "sql",count(*),sum(executions) "totexecs"
 fromv$sqlarea
whereexecutions<5
groupbysubstr(sql_text,1,80)
havingcount(*)>30
orderby2;
--游标的观察
setpages300;
selectsum(a.value), b.name
 fromv$sesstat a, v$statname b
wherea.statistic#=b.statistic#
  andb.name='opened cursors current'
groupbyb.name;
selectcount(0)fromv$open_cursor;
selectuser_name, sql_text,count(0)
 fromv$open_cursor
groupbyuser_name, sql_text
havingcount(0)>30;
--查看当前用户&username执行的SQL
selectsql_text
 fromv$sqltext_with_newlines
where(hash_value, address)in
       (selectsql_hash_value, sql_address
         fromv$session
        whereusername='&username')
orderbyaddress, piece;