ORACLE 深入解析10053事件
新年新说：新年伊始，2012年过去了，我们又踏上了2013年的，回顾2012我们付出了很多，辛勤和汗水换来了知识和友谊，当我们技术成长的时候我才发现长路漫漫，唯心
新年新说：
新年伊始，2012年过去了，我们又踏上了2013年的，回顾2012我们付出了很多，辛勤和汗水换来了知识和友谊，当我们技术成长的时候我才发现长路漫漫，唯心可敬。一份耕耘一份收获，走技术之路是艰辛的 孤独的 漫长的，在此向刚入门的小伙子们，说一说心得体会。做好心理准备，可能你为了小小的虚荣心，为了生活所迫，才走上此路，但你也要走的洒脱 走的稳健，当你站在第一个里程碑时回顾来时路，你会发现你的收获是值得的，你的付出是有意思的，你才能有继续走下去的勇气。我要感谢 Alantany tigerfish 海哥 张老师 飚哥 寅总 dingjun 晶晶 童mm 蓓蓓 还有 好多好多 帮助过我的人们，我的成长离不开你们的鼓励。飙完泪之后开始上干货吧：）
ORACLE 深入解析10053事件
本次我们主要讲解oracle 10053事件和实验，好多朋友可能对这个事件不是很熟悉，因为在日常运维中用到的不是很多。Oracle 10046和10053 都是非官方trace sql的方法，在官方文档上是找不到相关资料的，但在MOS上可以找到。sql_trace是官方推荐的trace sql的方法，在官方文档上是可以查询出来的。
10053事件：用来描述oracle如何选择执行计划的过程，然后输出到trace文件里，共我们参考，因为我们经常看执行计划怎么执行的消耗了哪些资源，而不是常看执行计划怎么选择出来了的。
10053场景：当SQL语句执行时走的是错误的执行计划，而又找不到原因时，这时请用10053来分析一下原因。
10053特点：
（1）只可以了解oracle执行计划的选择过程
（2）无法获知代价的计算公式，因为这是oracle内部的商业机密，美国服务器，而且每个oracle版本的优化器计算公式都不相同差距还是蛮大的，不同版本的同一个语句的代价也不一样，优化器现在还不是很成熟，还有待完善。
（3）在这个里面我们重点要了解的是“代价”是如何计算出来的，然后我们才能了解执行计划是如何选择的。
（4）在10053中可以了解哪些因素影响sql的执行代价
（5）oracle 8i cost等价IO资源消耗 9i以后cost等价IO+CPU+网络+等待事件+其他代价
一般IO资源的权重比较大 CPU权重较小
10053内容：
参数区：初始化参数，隐含参数，这些参数可以左右oracle工作方式
SQL区：执行的SQL语句，是否使用绑定变量，是否进行了转换操作
系统信息区：操作系统统计信息 cpu主频 CPU执行时间 IO寻址时间 单块读时间 多块读时间
对象统计信息区：
数据访问方式：访问方式不一样计算代价的方法也不一样，全表扫描 走索引 多表关联 代价都不同
关联查询：把每张表都作为驱动表去组合，择优选择“代价”最小的关联方式，与哪个表在前无关系
代价的最后修正：oracle会对选择出来的代价再进行最后的修正，使其更准确一些，更合理一些
选择出最终执行计划：这个过程是非常快速的，毫秒级就搞定啦
实验环境
LEO1@LEO1> select * from v$version; 这是我的oracle edition
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
1.验证全表扫描的成本计算公式，贴出执行计划和计算公式。
LEO1@LEO1> col sname for a20
LEO1@LEO1> col pname for a20
LEO1@LEO1> col pual1 for a30
LEO1@LEO1> col pual2 for a30
LEO1@LEO1> select * from sys.aux_stats$; 查看操作系统统计信息
SNAME PNAME PVAL1 PVAL2
-------------------- -------------------- ---------- ---------------------------------------------------
SYSSTATS_INFO STATUS COMPLETED
SYSSTATS_INFO DSTART 08-15-2009 00:49
SYSSTATS_INFO DSTOP 08-15-2009 00:49
SYSSTATS_INFO FLAGS 1
SYSSTATS_MAIN CPUSPEEDNW 2657.0122
SYSSTATS_MAIN IOSEEKTIM 10
SYSSTATS_MAIN IOTFRSPEED 4096
SYSSTATS_MAIN SREADTIM
SYSSTATS_MAIN MREADTIM
SYSSTATS_MAIN CPUSPEED
SYSSTATS_MAIN MBRC
SYSSTATS_MAIN MAXTHR
SYSSTATS_MAIN SLAVETHR
说明
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