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Performance tuning

Posted on 2014-03-06
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Last Modified: 2014-06-10
How do we know if we have to build a new index or gather statistics to improve the performance ...

Is there anyway, Oracle automatically gathers statistics or do we have to do it manually.
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Question by:d27m11y
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slightwv (䄆 Netminder) earned 672 total points
ID: 39911366
>>How do we know if we have to build a new index or gather statistics to improve the performance ...

It may sound simplistic but:  People complain?

Check the server:  Is a lot of CPU being used?  A lot of disk I/O, Memory?

If you are licensed for the Performance Pack in Enterprise Manager there are a lot of Advisors that will go through how your database is being used and make recommendations.

If you aren't licensed for it, StatsPack is a decent second place but requires you to go through the output and understand what you are seeing.

Many DBA's have their own things to look at.

I used to look in v$sql for disk reads and see what I could do about the SQL causing them.

>>Is there anyway, Oracle automatically gathers statistics or do we have to do it manually.

Look in the online documentation for your specific version of Oracle for he automatic maintenance window.
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by:David
David earned 664 total points
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Needing a new index.....  a study of the resource-intensive SQL statements (explain plans) should point out if people are doing full table scans.  Said tables are likely candidates for better indexing.  Improper use of block sizes, contention (locked rows), and parallelism are worth a look-over as well.

In 11g and higher, Oracle has eliminated the need for scripted stats updates, as slightwv alludes to.  Somewhat like Microsoft's services, the database is now self-aware when a table or index stats need to be checked.  There are numerous settings a knowledgeable DBA can tweak, but the old way of doing this is gone.
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by:Mark Geerlings
Mark Geerlings earned 664 total points
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Yes, In Oracle10g and 11g databases, Oracle will likely gather some statisics for you automatically.  Are these (default) statistics always the best ones for your database and your application/  Likely no.

What klnd of application do you have?  Is it purchased or custom?

Is it mainly transaction-processing or reporting (Data Warehouse)?

Are your init parameters adjusted for your hardware and application?
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by:d27m11y
ID: 39940820
It is a custom application and OLTP environment.
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by:Steve Wales
ID: 40124009
This question has been classified as abandoned and is closed as part of the Cleanup Program. See the recommendation for more details.
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