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摘要: 本章主要就是讲解,Oracle提供了哪些手段让我们的访问速度更快!ObjectivesAfter completing this lesson,you should be able to do the following:Compare and evalate the different storage structuessExamine different data access methodsImplement different partitionion methodsData Storage Structures最最普通的表集群表(将几个相互关联的表,一起放在一个块里面,读写的时候只进 阅读全文
posted @ 2013-05-08 19:12 ArcerZhang 阅读(195) 评论(0) 推荐(0) 编辑
摘要: Index ReorganizationIndexes on volatile tables are a performance problem.Only entirely empty index blocks go to the free list.If a block contains only one entry,it must be maintained.You may need to rebuild indexes.Monitoring Indexes SpaceTo collect usage statistics regarding an index:(搜集索引的相关数据)SQL 阅读全文
posted @ 2013-05-08 18:37 ArcerZhang 阅读(293) 评论(0) 推荐(0) 编辑
摘要: Database Block SizeMinimize block visits by:Using a large block sizePacking rows tightlyPreventing row migrationPacking rows tightly与Preventing row migraion是一对矛盾体.如果packing rows tightly过量,就会导致row migration.DB_BLOCK_SIZE ParameterThe database block size:Is defined by the DB_BLOCK_SIZE parameter.Is se 阅读全文
posted @ 2013-05-08 16:56 ArcerZhang 阅读(186) 评论(0) 推荐(0) 编辑
摘要: Locally Managed ExtentsCreate a locally managed tablespace:(以后所有的表空间管理方式都需要使用Locally managed method)SQL>CREATE TABLESPACE user_data_1DATAFILE '/u01/oradata/sid_name/1m_1.dbf'SIZE 100MEXTENT MANAGEMENT LOCALUNIFORM SIZE 2M;With the Oracle database the default extent management is local.Pro 阅读全文
posted @ 2013-05-08 14:44 ArcerZhang 阅读(361) 评论(0) 推荐(0) 编辑
摘要: ObjectivesAfter completing this lesson,you should be able to do the following:Use automatic segment space managementUse manual segment space managementDescribe the use of Oracle block parametersRecover space from sparsely populated segmentsDescribe and detect chaining and migration of Oracle blocksP 阅读全文
posted @ 2013-05-08 11:33 ArcerZhang 阅读(189) 评论(0) 推荐(0) 编辑
摘要: Using System StatisticsSystem statistics enable the CBO to use CPU and I/O characteristics.System statistics must be gathered on a regular basis;this does not invalidate cached plans.Gathering system statistics equals analyzing system activity for a specified period of time.所有的System Statistics 信息,都 阅读全文
posted @ 2013-05-07 18:48 ArcerZhang 阅读(152) 评论(0) 推荐(0) 编辑
摘要: Generating HistogramsHistogram statistics are generated by:SQL>EXECUTE dbms_stats.gather_table_stats('HR','EMPLOYEES',METHOD_OPT => 'FOR COLUMNS SIZE 10 salary') ;Histograms are specified using the METHOD_OPT argument of the DBMS_STATS gathering procedure.Oracle recomme 阅读全文
posted @ 2013-05-07 17:52 ArcerZhang 阅读(228) 评论(0) 推荐(0) 编辑
摘要: Skewed Data分析上述SQL语句,如果查询的数据很多,多到接近于整张表的数据了,那这个时候查询最优执行计划,就是全表扫描(full scan);如果查询的数据不是很多,此时就最好按照索引查询.数据的分布不同,最优的执行计划也不相同. 阅读全文
posted @ 2013-05-07 16:54 ArcerZhang 阅读(128) 评论(0) 推荐(0) 编辑
摘要: 总结Table statistics ---> DBA_TABLES;获取Table statistics,通过DBA_TABLES 数据字典SQL> cldesc DBA_TABLES; Name Null? Type ----------------------------------------- -------- ---------------------------- OWNER NOT NULL VARCHAR2(30) TABLE... 阅读全文
posted @ 2013-05-07 15:32 ArcerZhang 阅读(276) 评论(0) 推荐(0) 编辑
摘要: When to Gather Statistics在10g、11g里面,搜集statistics信息分自动和手工方式两种.Table StatisticsNumber of rowsNumber of blocks and empty blocksAverage available free spaceNumber of chained or migrated rowsAverage row lengthLast analyze date and smaple sizeData dictionary view:dba_tables查看表的统计信息,主要依据数据字典dba_tablesIndex 阅读全文
posted @ 2013-05-07 13:27 ArcerZhang 阅读(121) 评论(0) 推荐(0) 编辑
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