10g otomatik istatistik

Oracle optimizer tarafindan bir query’nin calistigi zaman en optimum yolu bulmak icin tablonun istatikleri dikkate alinir.

Ornek olarak

Select table_name,num_rows from user_tables;

employees 107 kayit gelmiş olsun.

Biz gun icerisinde bu employees tablosunda ciddi degisikler yapip kayit sayisini 2000000 kayida cikarip commit yaptigimizi dusunun.

tekrar yukaridaki sorgulamayi yaparsaniz tablomuzun hala 107 kayitli oldugu gozukecektir.

Aslinda select count(*) from employees yapsak 2000000 kayit donecektir.

iste bu noktada en ciddi sorun ortaya cikar yani optimizer 107 kayida gore bir plan cikarir.

bizim leventten 2 sokak yakimiza gidecegimizi dusunerek yuruyerek gitmeye karar vermemiz gibi.
Ama aslinda gidilecek yol cok daha fazla uzundur. Bu noktada yanlis plan yapilmistir belkide 10 dakikada gelebilecek sorgumuz 3 saate geri donus saglayabilir.

10 en azindan her gece otomatik istatistik alir.

bizim yapmamiz gereken statistic_level parametresini kontrol etmemiz ve basic olmamasini gormemiz gerekir.

Ama yinede gun icinde istatikde almamiz gerekir bu durumda DBMS_stats paketini kullanarak employees tablosunun istatiklerini alip dogru plani olusturmasini saglayabiliriz.

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About oracledocuments

Zekeriya Beşiroğlu, It joined the Bilginc IT Academy in July 2000. In the meantime, the Oracle Education, Oracle Data Base Management System and Oracle Internet Technologies, Oracle development technologies such as the training of Oracle products is responsible for training as consultants. During this task, since 1 April 2008 with 293 Oracle training in total, in 2150 Oracle customers successfully submitted. Oracle 10g New York in November 2002 have received training and education in Turkey was the first time the consultants. 20 April 2008 on education in Turkey 11g is the first who was a consultant. Oracle Real Application Cluster Expert advisor is certified is the first . Http://zekeriyabesiroglu.blogspot.com and Http://www.oracleforum.info owner and manager of the site. Its own has more than one hundred articles. In addition, creation and improvement of training materials are also related to work. Oracle products are used, database management and reporting Academy eruditely It also is working on. From the date of 1 January 2009 will continue to work as the Technical Director
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