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http://www.sun.com/blueprints/0303/817-1781.pdf

Create virtual indexes 11:42:42 CS@UOCQA:-> create index index_1 on BSKT_SHOPPING_BASKET_ITEM (BASKET_RECIPIENT_ID, BASKET_ITEM_ID) nosegment; need to set a hidden parameter as following. 11:42:42 CS@UOCQA:-> alter session set “_use_nosegment_indexes”=true; Indexes created without any segment. cannot views with User_indexes. Can be viewed in USER_OBJECTS. Useful in producton environment where we cannot create any indexes. Existance of this index…

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(1) Operation : SORT UNIQUE Cause : DISTINCT Clause, and IN sub-query where subquery is independent meand no co-relation with parenst query. If for IN subquery, there is an unique index on selected columns then SORT UNIQUE can be avoided. (2) Operation : SORT AGGREGATE Cause : Whenever u use group functions. It does not…

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select a.ksppinm “Parameter”, b.ksppstvl “Session Value”, c.ksppstvl “Instance Value” from x$ksppi a, x$ksppcv b, x$ksppsv c where a.indx = b.indx and a.indx = c.indx and substr(ksppinm,1,1)=’_’ order by a.ksppinm;

spool badsql5 set lines 132 set pages 300 col USR format a14 col PAR heading “Parsing ID” format 9999999 col ELA heading “ELP time(Sec)” format 9999999.0 col HASH heading “Hash Value” col USR heading “Parsing User” col T heading “SQL Text having Elapsed time > 1 sec” break on HASH on USR on ELA skip…

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http://www.adp-gmbh.ch/ora/misc/x.html http://www.orafaq.com/faqdbain.htm

Histograms ========== For uniformly distributed data, the cost-based approach makes fairly accurate guesses at the cost of executing a particular statement. However, when the data is not uniformly distributed, the optimizer cannot accurately estimate the selectivity of a query. Beginning in release 7.3, for columns which do not have uniform data distribution, Oracle will allow…

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