ORA-19815: WARNING: db_recovery_file_dest_size of 5218762752 bytes is 100.00% used, and has 0 remain
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今天一个同学问的一个有关数据库的问题，我看了一下alert日志，发现有以下报错信息。现记录下来，以备后用ORA-19815: WARNING: db_recovery_file_dest_size of 5218762752 bytes is 100.00% used, and has 0 rema... 阅读全文
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AWR能够帮助DBA识别占用资源最多的SQL语句.SQL Tune Advisor执行步骤捕获到占用资源较多的SQLAdvisor对捕获到的、占用资源较多的SQL进行分析Advisor产生建议的SQL执行实施SQLSQL Tuning Advisor:OverviewAutomatic SQL Tuning:OverviewAutomatic SQL Tuning automates the entire SQL tuning process and replaces manual SQL tuning.Optimizer modes:Normal modes:Tuning mode or A 阅读全文
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oracle的智能体现:oracle在AWR执行完成一次快照收集之后，ADDM会自动监控本次收集快照之后发现的影响性能的SQL或者其他组件，然后自动调用相应的Advisor进行分析，被报告出分析结果.ObjectivesAfter completing this lesson,you should be able to :Use the SQL Tuning Advisor to:-Identify SQL statements that are using the most resources-Tune SQL statements that are using the most resou 阅读全文
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oracle搜集表的信息，并不是每张表都搜集,一下若干种情况，会被搜集到:统计信息是空的表，会被搜集达到一定比例的表，会被搜集在搜集表信息的时候，加上CASCADE关键字之后，就会搜集此表相关的索引等信息.Statistics Preferences:OverviewUsing Statistics PreferencesPUBLISH:Used to decide whether to publish the statistics to the dictionary or to store them in a pending area before.publish the statistic 阅读全文
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Optimizer Statistics CollectionWays to collect statistics:-Automatically:Automatic Maintenance Tasks（自动搜集统计数据信息的功能，是自oracle10g以后才有的）查看系统里的job信息SQL> select owner,job_name from dba_scheduler_jobs;OWNER JOB_NAME------------------------------ ------------------------------SYS ... 阅读全文
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1、analyze table emp1 compute statistics;2、dbms_stats package搜集系统的统计信息:dbms_stats.gahter_system_stats 阅读全文
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/* 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
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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
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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
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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