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Downgrading Oracle - Downgrade tips

Oracle Database Tips by Donald Burleson



Question: I need to downgrade my oracle database from to

The closest instructions I can find is the 10g Release 2 (Downgrading a Database Back to the Previous Oracle Database Release) guide.

As for compatibility, it says "If the compatibility level of your release 10.2 database is 10.2.0 or higher, then you will not be able to downgrade."


I get . Does this mean I won't be able to downgrade Oracle?

Am I looking at the right documentation ?


Answer: First, see MOSC note 398372.1 (Downgrading The Database From 10.2.0 To Lower Releases).  If your COMPATIBLE parm is at 10.2, then you were using 10.2 features and you cannot downgrade directly.

From Oracle? Database Upgrade Guide 10g Release 2 (10.2)

When you upgrade to a new release of the Oracle Database, certain new features may make your database incompatible with your previous release. Your upgraded Oracle database becomes incompatible with your previous release under the following conditions:

A new feature stores any data on disk (including data dictionary changes) that cannot be processed with your previous release.

An existing feature behaves differently in the new environment as compared to the old environment. This type of incompatibility is classified as a language incompatibility.

The COMPATIBLE Initialization Parameter

The Oracle Database enables you to control the compatibility of your database with the COMPATIBLE initialization parameter. By default, when the COMPATIBLE initialization parameter is not set in your parameter file, it defaults to 10.2.0 for Oracle Database 10g release 10.2. You cannot use new Oracle Database 10g features that would make your upgraded database incompatible until the COMPATIBLE initialization parameter is set to this value.

Table 5-1 illustrates the default value and the range of values of the COMPATIBLE initialization parameter in the new Oracle Database 10g release and in each release supported for upgrading to the new Oracle Database 10g release.

Table 5-1 The COMPATIBLE Initialization Parameter

Oracle             Default  Min        Maximum
          Release  Value    Value      Value

Oracle8i  8.1.7    8.0.0  8.1.7.x.x
Oracle9i  9.0.1    8.1.0  9.0.1.x.x
Oracle9i  9.2      8.1.0  9.2.0.x.x
Oracle10g 10.1    10.0.0  10.1.0.x.x
Oracle10g 10.2    10.2.0  10.2.0.x.x

The Oracle? Database Upgrade Guide 10g Release 1 (10.1) has directions for downgrading Oracle:

Downgrade the Oracle Database

Make sure your database is compatible with the release to which you are downgrading before you perform the downgrade steps in this section.

Complete the following steps to downgrade your release 10.1 database to the previous Oracle Database release:

Log in to the system as the owner of the release 10.1 Oracle home directory.

  1. At a system prompt, change to the ORACLE_HOME/rdbms/admin directory.

  2. Start SQL*Plus.

  3. Connect to the database instance as a user with SYSDBA privileges.

  4. Start up the instance in DOWNGRADE mode:


You may need to use the PFILE option to specify the location of your initialization parameter file.

Set the system to spool results to a log file for later verification of success:

SQL> SPOOL downgrade.log

Run dold_release.sql, where old_release refers to the release to which you are downgrading. See Table 7-1 to choose the correct script. Each script provides a direct downgrade to the release specified in the "Downgrading To" column.

To run a script, enter the following:

SQL> @dold_release.sql

If you like Oracle tuning, see the book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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