Solved

cbo optimer

Posted on 2013-01-07
5
227 Views
Last Modified: 2013-01-10
In a simple way what is the meaning of cost base optimizer..
0
Comment
Question by:walkerdba
5 Comments
 
LVL 76

Expert Comment

by:slightwv (䄆 Netminder)
ID: 38753243
It is code that uses statistics to choose the best execution plan for whatever the task is.

The old way was rule based.  It had strict rules to follow.  For example, if an index exists, use it no matter what.

The problem here is at times using an index will actually slow down the execution.

See if this helps fill in the gaps:
http://www.dba-oracle.com/art_otn_cbo.htm
0
 
LVL 23

Expert Comment

by:David
ID: 38753368
Hi walker, for every statement, the Oracle system will attempt to optimize the execution cost.  As slight mentioned, statistics provide the metadata used to evaluate the size and distribution of data.

Is that simple enough? <grins>
0
 
LVL 37

Accepted Solution

by:
Geert Gruwez earned 500 total points
ID: 38753711
it's all in the words
optimize the work based on the cost
the work is the exection of a query following a certain plan
every step in the plan has a certain cost
the best plan usually has the lowest cost

your next question could be what is a hard parse ...
hard parse is working out that execution plan
0
 
LVL 8

Expert Comment

by:ReliableDBA
ID: 38756172
Let me see if i can provide any inputs here.

In a simple way what is the meaning of cost base optimizer..
  => when we go to a market to buy something, we choose a product of low cost(ofcourse, not compromising on the quality).
  => Similarly, Oracle calculates the cost(for each unit of operation viz. performing a full table scan/index unique scan/range scan etc., )and gives us each step in the execution plan and the the cost associated with it.

Just my 2 cents.
0
 

Author Closing Comment

by:walkerdba
ID: 38765207
yes
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Truncate is a DDL Command where as Delete is a DML Command. Both will delete data from table, but what is the difference between these below statements truncate table <table_name> ?? delete from <table_name> ?? The first command cannot be …
From implementing a password expiration date, to datatype conversions and file export options, these are some useful settings I've found in Jasper Server.
This video shows setup options and the basic steps and syntax for duplicating (cloning) a database from one instance to another. Examples are given for duplicating to the same machine and to different machines
This video shows how to configure and send email from and Oracle database using both UTL_SMTP and UTL_MAIL, as well as comparing UTL_SMTP to a manual SMTP conversation with a mail server.

863 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

22 Experts available now in Live!

Get 1:1 Help Now