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ROBO BOOKS MONOGRAPHDATA WAREHOUSING AND ORACLE8I• APPEND• NOAPPEND• PARALLEL_INDEXAn example would be:SELECT /*+ FULL(clients) PARALLEL(clients,5,3)*/ client_id, client_name,client_address FROM clients;By using hints the developer and tuning DBA can exercise a high level of controlover how a statement is processed using the parallel query option.Oracle8 Enhanced Optimizer FeaturesThe Optimizer in Oracle8 has been dramatically improved to recognize andutilize partitions, to use new join and anti-join techniques and in general to do abetter job of tuning statements.Oracle8 introduces performance improvements to the processing of star queries,which are common in data warehouse applications. Oracle7 introduced thefunctionality of star query optimization, which provides performanceimprovements for these types of queries. In Oracle8, star-query processing hasbeen improved to provide better optimization for star queries.In Oracle8, a new method for executing star queries was introduced. Using amore efficient algorithm, and utilizing bitmapped indexes, the new star-queryprocessing provided a significant performance boost to data warehouseapplications.Oracle8 has superior performance with several types of star queries, includingstar schemas with "sparse" fact tables where the criteria eliminate a greatnumber of the fact table rows. Also, when a schema has multiple fact tables, theoptimizer efficiently processes the query. Finally, Oracle8 can efficiently processstar queries with large or many dimension tables, unconstrained dimensiontables, and dimension tables that have a "snowflake" schema design.Oracle8's star-query optimization algorithm, unlike that of Oracle7, does notproduce any Cartesian-product joins. Star queries are now processed in twobasic phases. First, Oracle8 retrieves only the necessary rows from the facttable. This retrieval is done using bit mapped indexes and is very efficient. Thesecond phase joins this result set from the fact table to the relevant dimensiontables. This allows for better optimizations of more complex star queries, such asthose with multiple fact tables. The new algorithm uses bit-mapped indexes,which offer significant storage savings over previous methods that requiredCOPYRIGHT © 2003 RAMPANT TECHPRESS. ALL RIGHTS RESERVED.PAGE 24