How to check conflicts while applying CPU patch?

How to check conflicts while applying CPU patch?

most of the times, we will never check any conflicts for the patches when applying any CPU. ofcourse this conflict checking command is not there even in README.html file that is distributed with patch.

Please use below command to check the conflicts aganist the oracle_home and avoid to land in problems

step 1: unzip your patch zip file
step 2: run below command
$ORACLE_HOME/OPatch/opatch prereq CheckConflictAgainstOHWithDetail -phBaseDir <patch_directory>

Example:

$ unzip p9655017_10204_linux.zip
$ $ORACLE_HOME/OPatch/opatch prereq CheckConflictAgainstOHWithDetail -phBaseDir 9655017
The other day, when I am doing patching on a RAC database, after executing the above conflict command, got below error

Following patches have conflicts. Please contact Oracle Support and get the merged patch of the patches :
6600051, 8836683
Whenever you get this type of error message, plz contact oracle support by raising a service request(SR)

In my case, Oracle support suggested to apply a merge patch 9347333 before applying Jul CPU 2011. Once done with applying merge patch, without any further issues I successfully applied CPU patch

Sometimes apart from above message you may see below warning messages which you can ignore

Summary of Conflict Analysis:

Patches that can be applied now without any conflicts are :
10013975, 10014009, 10014012, 10014015, 10325878, 10325885, 11787762, 11787763, 11787765, 11787766, 12419249, 12566121, 12566124, 12566126, 12566129, 12566131, 12566134, 12566136, 12566137, 12566139, 12566141, 12566142, 12566143, 7155248, 7155249, 7155250, 7155251, 7155252, 7155253, 7155254, 7197583, 7375611, 7375613, 7375617, 7609057, 8309592, 8309632, 8568395, 8568397, 8568398, 8568402, 8568404, 8836667, 8836671, 8836675, 8836677, 8836678, 8836683, 8836684, 8836686, 9173244, 9173253, 9442328, 9442331, 9442339, 9678690, 9678695, 9678697

Following patches are not required, as they are subset of the patches in Oracle Home or subset of the patches in the given list :
10249540, 8836681, 8568405

Following patches will be rolled back from Oracle Home on application of the patches in the given list :
10013975, 10014009, 10014012, 10014015, 10325878, 10249540, 8836681, 8568405, 7155248, 7155249, 7155250, 7155251, 7155252, 7197583, 7375611, 7375613, 7375617, 7609057, 8309592, 8309632, 8568395, 8568397, 8568398, 8568402, 8568404, 8836667, 8836671, 8836675, 8836677, 8836678, 8836683, 8836684, 8836686, 9173244, 9173253, 9442328, 9442331, 9442339, 9678690, 9678695