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9i有一个新的包 dbms_xplan，对查询plan_table表是一个很有用的工具，相对于以前写一个复杂的SQL语句，然后从plan_table看执行计划，不如调用 dbms_xplan 包，还可以显示格式，这个工具的使用也非常方便。调用的语法类似select * from table(dbms_xplan.display(format=>'BASIC')) 使用 TABLE() 操作符，或者 CAST 操作。DISPLAY 函数有三个参数TABLE_NAME 指出优化计划放在哪个表里面，默认是 PLAN_TABLE. STATEMENT_ID 指的是plan tab 阅读全文
posted @ 2007-06-22 17:20 徐正柱- 阅读(524) 评论(0) 推荐(0) 编辑
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buffer busy waits说明buffer cache中有一些buffers被多个进程尝试同时访问。查看V$WAITSTAT观察各种类型buffer wait的统计信息。SELECT class, count FROM V$WAITSTAT WHERE count > 0 ORDER BY count DESC;也可以查看V$SESSION_WAIT观察当前buffer wait信息,其中P1-FILE_ID, P2- BLOCK_ID,再通过DBA_EXTENTS查找哪些SEGMENT被争用。Select * from v$session_wait where event=’b 阅读全文
posted @ 2007-06-22 17:12 徐正柱- 阅读(995) 评论(0) 推荐(0) 编辑
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1.查询记录相同的其中一笔记录SELECT mat12id, mat12name , bat22id,PRICEFROM (SELECT mat12id, mat12name , bat22id,PRICE, ROW_NUMBER() OVER (PARTITION BY mat12id ORDER BY bat22id DESC) RN FROM bat22)WHERE RN = 12.查询从多少行到多少行的记录SELECT * FROM (SELECT A.*,rownum rFROM(SELECT * FROM TableName )AWHER... 阅读全文
posted @ 2007-06-22 11:24 徐正柱- 阅读(947) 评论(0) 推荐(0) 编辑
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Q. 1 : When will the rollback information applied in the event of a database crash 1. before the crash occurs 2. after the recovery is complete 3. immediately after re-opening the database bef... 阅读全文
posted @ 2007-06-20 17:54 徐正柱- 阅读(670) 评论(0) 推荐(0) 编辑
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注：答案在选项后面 Q. 1 : The default tablespace clause in the create user command sets the location for 1. Database Objects created by the user 2. Temporary Objects Created By the User 3. System Ob... 阅读全文
posted @ 2007-06-20 17:46 徐正柱- 阅读(391) 评论(0) 推荐(0) 编辑
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Q. 1 : What feature in oracle allows you to monitor Suspicious Activity on the Datbase 1. Replication 2. Auditing 3. Monitoring 4. Tuning Q. 2 : Auditing can be turned on by setting this... 阅读全文
posted @ 2007-06-20 17:40 徐正柱- 阅读(323) 评论(0) 推荐(0) 编辑
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Q. 1 : The Database must be in this mode for the instance to be started 1. MOUNT 2. OPEN 3. NOMOUNT 4. None 3 Q. 2 : When Oracle startups up, what happens if a datafile or redo log file n... 阅读全文
posted @ 2007-06-20 17:38 徐正柱- 阅读(554) 评论(0) 推荐(0) 编辑
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Q. 1 : This symbol, When you put infront of a line in the parameter file, signifies a comment 1. $ 2. @ 3. # 4. ! 3 Q. 2 : When you change a parameter value in the parameter file, when wil... 阅读全文
posted @ 2007-06-20 17:37 徐正柱- 阅读(343) 评论(0) 推荐(0) 编辑
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Q. 1 : What system privilege is required to create a rollback segment ? 1. Create database 2. Create rollback segment 3. Alter database 4. Create segment 2 Q. 2 : Oracle recommends ... 阅读全文
posted @ 2007-06-20 17:35 徐正柱- 阅读(301) 评论(0) 推荐(0) 编辑 |
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