Is it possible to downgrade oracle 11.1.0.6.0 to 10.2.0.4.0? 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
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.