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绍Oracle数据库的优化之数据库磁盘I/Ohttp://doc.chinaunix.net/oracle/200905/208827.shtmlv$filestat ,v$latch, v$queue, v$shared_server v$waitstat[@more@]

public stored in schema of outln.dic table: ol$, ol$hintskey knowledge:signature column of ol$. It is similar as sql hash value but with some different characteristic:1, space char and line-feed char are not including to calculated signature.2, Upper case and lower case of a character get the same signature value.---- optimize sql by outline method guide.1, create current sql outline .2, tune sql code until be satisfied with the performance. Some skill can used in this stage: 1>use sql hints

-- 看来，学习还是要时常牢记那句话：纸上得来终觉浅，绝知此事要躬行。http://yong321.freeshell.org/oranotes/Histogram.htmlhttp://www.oracle.com.cn/viewthread.php?tid=67935表字段柱状图的理解：-- dictionary : dba_tab_col_statistics/user_tab_col_statisticsdba_tab_histogram/user_tab_histogram-- definition:the definition name is base the meaning of column endpoint_number.1， 当字段列DISTINCT VALUE>255 时，只能建立HBH(HEIGHT-BALANCED)HISTOGRAM. 即：平衡树。here endpoint_number is stand for card-weight

http://www.bitscn.com/pdb/oracle/200809/151545.htmlRESOLVE METHOD:CHECK EXECUTE PLAN:SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY); 1, CHECK IF THERE IS CARTESIAN .2，CHECK TABLE STATISTICS.3, IF USE PREDICT FILTER ON TABLE, THEN CHECK COLUMN STATISTICS .4, UPDATE TABLE STATISTICS. SQL> EXEC DBMS_STATS.DELETE_TABLE_STATS(USER, 'ORD_HIT_COMM') 　　PL/SQL procedure successfully completed. 　　SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS(USER, 'ORD_HIT_COMM') 　　PL/SQL procedure successfully completed.

unnest, no_ununest, push_subq --- sub querypush_pred, merge, no_merge --- viewshttp://bbs.chinabyte.com/thread-357284-1-1.htmlsql 性能变差原因及办法:http://www.laoxiong.net/how-keeping-sql-plan-stability.htmlrecovery :http://xuqingwei.itpub.net/post/37188/500757[@more@]

analyze index t_test1_idx1 validate structure;会话视图 index_statsalter index pk_emp monitoring usage ;全局视图 v$object_usage [@more@]INDEX_STATS" stores information from the lastANALYZE INDEX ... VALIDATE STRUCTUREstatement.上面语句意思是说index_stats存储最后一次对索引分析结构的信息.判断一个所以是否需要重建，我们介绍一个简单的方法：对一个索引进行结构分析后，如果该索引占用超过了一个数据块，且满足以下条件之一：B-tree树的高度大于3；使用百分比低于75%；数据删除率大于15%，就需要考虑对索引重建：