Re: Are there performancebenefits to reorganizing database-using export/import?

From: Charles Hooper <>
Date: Mon, 10 Nov 2008 14:25:17 -0800 (PST)
Message-ID: <>

On Nov 10, 3:52 pm, wrote:
> I am using Oracle on HP UNIX 11i. Since it is a production
> system, I cannot change version of Oracle any time soon, so please do
> not suggest that.
> I have a production database using Oracle, which has been
> running for last 3 years since it was upgraded from 8.1.7. At that
> time we had done full export of 8.1.7 database and then created 9.2.
> instance and then imported all the application schemas.
> Load on our database has been increasing and there are constant
> pressures from management to improve performance. We have looked at
> indexes many times, have lots of memory for SGA and have tuned various
> init.ora parameters. We utlize three pools buffer, keep and recycle.
> Being a third party packages, we cannot rewrite queries. Avg CPU
> Utilization (6 CPU"s) is 30%, memeory utilization is 60% (we have 24
> GB memeory on the server), so I do not see we are taxing any
> resources, i..e, adding more CPU's and memory should not help.
> Application is a mix of OLTP and reporting, it is definitely more read
> than write.
> Are there any benefits to reorganize database using export/import,
> i.e., we will do a full export of existing database and then delete
> all objects from application schemas and do schema imports. We will
> run the dbms_Stats again to recomputed statistics. Of course, we will
> test all of that in a test environment before making change sin
> production.
> I have heard different views on reorganization. Some people say it is
> useless, some people say it can improve performance since data will be
> compacted in fewer blocks.
> Appreciate your feedback.

In agreement with Joel's post.

Zigzag, there are some warnings about doing what you suggest, and those warnings are well defined in "Expert Oracle Database Architecture" (pages 340-341):

There are also a couple excellent threads on which warn about exporting your database, dropping the database, crossing your fingers, and importing.

What happens if you accidentally change the character set when you recreate the database and forget to generate an import log file? Data, are we missing rows? The empty set character in ASCII requires a single byte, but that same character requires more than one byte in other character sets. So, what happens when a column is defined as VARCHAR2(30) and an existing row contains a column value that is exactly 30 characters long with an empty set character in the column data?

What happens if you accidentally transfer the export file using ASCII FTP before trying to import the file (from its transferred to location).

You must consider the risks before proceeding.

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Mon Nov 10 2008 - 16:25:17 CST

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