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发布时间:2005-03-31 13:17:29

please correct me if my understanding is wrong.LIO - from/to the buffer cache ( not disk ).PIO - to/from the disk.correct ?in many of the threads on tuning i notice that you mention, the less the number of PIO as well as LIO the better. i can understand the 'physical' part of it but not the logical.the query has to get the results and it has to do as much work as is necessary to get it, isnt it ? so at least that much of LIO is a must. how can we reduce that ? Followup: LIO = logical = buffer......【阅读全文】

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发布时间:2005-03-29 23:17:44

1. use dual table and connect by . ( 转载自 hotsos )SQL> @aaa.sqlSQL> with x as (  2           select trunc(sysdate,'YEAR') + rownum -1  3           from dual  4           connect by 1 = 1  5           and level <= add_months(trunc(sysdate,'YEAR'),12) - trunc(sysdate,'......【阅读全文】

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发布时间:2005-03-29 10:11:23

最近在itpub上看到这个帖子http://www.itpub.net/338792.html, 引发我下面要说的话. 1. :-) 楼主在描述问题的时候, 并没有将她/他遇到的问题描述清楚. 我在建实体化视图的时候个别create mv语句总是报ORA-01652: unable to extend temp segment by 1024 楼主并没有将他操作中遇到的实际的错误信息展示给我们,实际的错误信息,应该是这样的吧:-)下面我模拟一个空间不够的例子, 我们可以看到实际的错误应该是这样的.SQL> select bytes from user_segments where segment_name = 'T'; BYTES---------- 4194304SQL> crea......【阅读全文】

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发布时间:2005-03-28 18:43:22

我们的系统每天都有一张大表, 主要是用来做报表处理的. 这个表的字段数目相当多, 目前已经达到50多个字段了, 其中有40个是标志字段. 受oracle系统表设计的影响, 我想到一下的方法来出里对应的表.1. Oracle的相关系统表. 打开sql.bsq的原始文件, 我们随处可见Oracle的设计中, 尽量将相应的具有类西属性的字段通过数字的位数来进行处理, 而后又通过bitand与视图联合处理的方式显示给最终用户. 我下面要举的例子来自oracle的动态视图,v$sql_shared_cursor.SQL> set long 5000SQL> select view_definition 2 from v$fixed_view_def......【阅读全文】

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发布时间:2005-03-28 18:41:09

You Asked (Jump to Tom's latest followup)Hi TomI never really understood the usage of GROUPING_ID function in OTN.I heard it avoids using multiple GROUPING functions.Can you please illustrate with a small exampleThanks and we said...http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:18735507471922#18844335353167You use grouping_id with "grouping sets" or group by cube/rollup -- it tells you the level of aggregation.Consider, we'll show grouping sets, group b......【阅读全文】

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