Is it possible to downgrade oracle 11.1.0.6.0 to 10.2.0.4.0?

Question

Is it possible to downgrade oracle 11.1.0.6.0 to 10.2.0.4.0? The Compatible parameter need to be changed to "10.2.0"? Today I have Compatible set to 10.2.0.4.0.

It's not clear on support.oracle if I need to change or not. This document http://www.oracle.com/technetwork/database/upgrade/upgrade11gr2-downgrade-methods-179029.pdf

state:

The major restriction on the downgrade script is that it cannot be run if the COMPATIBLE parameter has been raised as part of, or after, the upgrade. This is because raising the COMPATIBLE parameter will allow on-disk changes that cannot be understood by the earlier version of Oracle Database. For this reason, downgrades from Oracle Database 11g Release 2 to Oracle Database 9i are not supported. Downgrades from Oracle Database 11g Release 2 to the following versions are supported:  10.1.0.5  10.2.0.2, 10.2.0.3, 10.2.0.4, 10.2.0.5  11.1.0.6, 11.1.0.7

but this one http://docs.oracle.com/cd/E11882_01/server.112/e17222/downgrade.htm#UPGRD12554

says:

If you are downgrading to Oracle Database 10g Release 2 (10.2), then the COMPATIBLE initialization parameter must be set to 10.2.0 or lower.

thx

Answer 1

The documentation is very confusing. Also, I figured out that we cannot set it to 10.2.0 (without digits) as answered by @Balazs, doing so will throw an error stating that the COMPATIBLE parameter is not correctly set. Changing it to 10.2.0.4 was possible and it was accepted by the dbase.

Answer 2

Yes, it is possible, as stated in the 11.1 documentation:

Supported Releases for Downgrading

Oracle mentions 10.2.0, because ideally you need not to set anything more specific (more digits). This is explained in:

How To Change The COMPATIBLE Parameter And What Is The Significance? (Doc ID 733987.1)

Use only the first 3 digits for the compatible parameter unless there would be some very specific instructions to do otherwise. Patch sets are normally not intended to add/change actual functionality, hence there is no need to increase the compatible parameter and set the 4th digit.

If you set it to 10.2.0.4.0, the downgrade should be still successful to version 10.2.0.4, but not anything lower.