摘要：
/* Oracle optimizer 执行选择方式原理分析*/select * from emp where empno=7369;oracle在执行查询计划的时候，并不是说要执行一次全表扫描和一次索引扫描之后，来决定到底是走哪一条路?而是通过数据字典里的统计数据信息，来分析判断到底是走那一条执行计划.|-full table|-index scandata_table---> num_rows(10000)-1/10000 num_rows(10000)-1/2SQL> create table emp1 as select * from emp;Table created.. 阅读全文
摘要：
Performance Tuning DataType of data gathered:Cumulative statistics:(自从instance启动以来的的数据，累加值)-Wait events with time information-Time model（基于时间模型的比较）Metrics:Statistics rates（度量指标）Sampled statistics:Active session history(样本指标)Statistics by sessionStatistics by SQLStatistics by serviceOther dimensions 阅读全文
摘要：
Instance TuningHave well-defined goalsAllocate memory to database structures.Consider I/O requirements in each part of the database.Tune the operating system for optimal performance of the database.Performance Tuning MethodologyThe tuning steps:Tune from the top down.Tune:1.The design2.The appliatio 阅读全文
摘要：
Managing Database PerformanceTuning ActivitiesThe three activites in perfomrance management are:Performance planningInstance tuningSQL tunningPerformance PlanningInvestment optionsSystem architetureScalabilityApplication design principlesWorkload testing,modeling,and implementationDeveloping new app 阅读全文